Fix mypy errors in pytorch_lightning/strategies/ddp.py

[lijm1358]

What does this PR do?

Fixes mypy typing errors in pytorch_lightning/strategies/ddp.py in #13445 .

src\pytorch_lightning\strategies\ddp.py:86: error: Function "builtins.callable" is not valid as a type  [valid-type]
src\pytorch_lightning\strategies\ddp.py:86: note: Perhaps you meant "typing.Callable" instead of "callable"?
src\pytorch_lightning\strategies\ddp.py:87: error: Function "builtins.callable" is not valid as a type  [valid-type]
src\pytorch_lightning\strategies\ddp.py:87: note: Perhaps you meant "typing.Callable" instead of "callable"?
src\pytorch_lightning\strategies\ddp.py:120: error: Value of type "Optional[List[device]]" is not indexable  [index]
src\pytorch_lightning\strategies\ddp.py:132: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:136: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:149: error: Item "None" of "Optional[ClusterEnvironment]" has no attribute "creates_processes_externally"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:150: error: Argument 1 to "_SubprocessScriptLauncher" has incompatible type "Optional[ClusterEnvironment]"; expected "ClusterEnvironment"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:159: error: Incompatible types in assignment (expression has type "object", variable has type "bool")  [assignment]
src\pytorch_lightning\strategies\ddp.py:163: error: Item "None" of "Optional[Accelerator]" has no attribute "setup"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:173: error: Argument 1 to "apply" of "LayerSync" has incompatible type "Optional[Module]"; expected Module  [arg-type]
src\pytorch_lightning\strategies\ddp.py:194: error: Argument 3 to "DistributedDataParallel" has incompatible type "**Dict[str, Union[Any, Dict[str, Any]]]"; expected "Union[int, device, None]"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:194: error: Argument 3 to "DistributedDataParallel" has incompatible type "**Dict[str, Union[Any, Dict[str, Any]]]"; expected "int"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:194: error: Argument 3 to "DistributedDataParallel" has incompatible type "**Dict[str, Union[Any, Dict[str, Any]]]"; expected "bool"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:194: error: Argument 3 to "DistributedDataParallel" has incompatible type "**Dict[str, Union[Any, Dict[str, Any]]]"; expected "float"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:196: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:196: note: Use "-> None" if function does not return a value
src\pytorch_lightning\strategies\ddp.py:234: error: Argument "model" to "register_ddp_comm_hook" has incompatible type "Optional[Module]"; expected "DistributedDataParallel"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:266: error: Item "None" of "Optional[object]" has no attribute "start_localSGD_iter"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:299: error: Argument 1 to "LightningDistributedModule" has incompatible type "Optional[Module]"; expected "Union[LightningModule, _LightningPrecisionModuleWrapperBase]"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:302: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:307: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:315: error: Return type "object" of "broadcast" incompatible with return type "TBroadcast" in supertype "Strategy"  [override]
src\pytorch_lightning\strategies\ddp.py:324: error: Item "None" of "Optional[LightningModule]" has no attribute "automatic_optimization"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:325: error: Argument 1 to "prepare_for_backward" has incompatible type "Optional[Module]"; expected "DistributedDataParallel"  [arg-type]
src\pytorch_lightning\strategies\ddp.py:327: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:327: note: Use "-> None" if function does not return a value
src\pytorch_lightning\strategies\ddp.py:331: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:331: error: Argument 3 of "reduce" is incompatible with supertype "Strategy"; supertype defines the argument type as "Union[ReduceOp, str, None]"  [override]
src\pytorch_lightning\strategies\ddp.py:331: note: This violates the Liskov substitution principle
src\pytorch_lightning\strategies\ddp.py:331: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
src\pytorch_lightning\strategies\ddp.py:347: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:349: error: "None" not callable  [misc]
src\pytorch_lightning\strategies\ddp.py:351: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:353: error: Item "None" of "Optional[LightningModule]" has no attribute "trainer"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:355: error: "None" not callable  [misc]
src\pytorch_lightning\strategies\ddp.py:358: error: Item "None" of "Optional[Module]" has no attribute "validation_step"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:358: error: "Tensor" not callable  [operator]
src\pytorch_lightning\strategies\ddp.py:360: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:362: error: Item "None" of "Optional[Module]" has no attribute "test_step"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:362: error: "Tensor" not callable  [operator]
src\pytorch_lightning\strategies\ddp.py:364: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:366: error: Item "None" of "Optional[Module]" has no attribute "predict_step"  [union-attr]
src\pytorch_lightning\strategies\ddp.py:366: error: "Tensor" not callable  [operator]
src\pytorch_lightning\strategies\ddp.py:368: error: Function is missing a return type annotation  [no-untyped-def]
src\pytorch_lightning\strategies\ddp.py:368: note: Use "-> None" if function does not return a value
src\pytorch_lightning\strategies\ddp.py:409: error: Incompatible types in assignment (expression has type "object", variable has type "Optional[str]")  [assignment]
src\pytorch_lightning\strategies\ddp.py:447: error: Item "None" of "Optional[List[int]]" has no attribute "__iter__" (not iterable)  [union-attr]
src\pytorch_lightning\strategies\ddp.py:461: error: "Tensor" not callable  [operator]
src\pytorch_lightning\strategies\ddp.py:478: error: Argument 1 to "revert" of "LayerSync" has incompatible type "Optional[Module]"; expected Module  [arg-type]
Found 44 errors in 1 file (checked 240 source files)

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[lijm1358]

Also, thank you for review & feedback, @rohitgr7, @awaelchli 😀

[codecov]

Codecov Report

Merging #13885 (22cf941) into master (d072e44) will increase coverage by 15%.
The diff coverage is 73%.

❗ Current head 22cf941 differs from pull request most recent head 5090579. Consider uploading reports for the commit 5090579 to get more accurate results

@@            Coverage Diff            @@
##           master   #13885     +/-   ##
=========================================
+ Coverage      61%      76%    +15%     
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  Files         324      341     +17     
  Lines       26342    26652    +310     
=========================================
+ Hits        16141    20268   +4127     
+ Misses      10201     6384   -3817