improve error msg of invalid input types (#1083)

Summary:
Discussed in #1077 (comment) , improving the error message of invalid `inputs` to tell the two types we allow: `Tensor` and `tuple[Tensor]`

Pull Request resolved: #1083

Reviewed By: vivekmig

Differential Revision: D41795064

Pulled By: aobo-y

fbshipit-source-id: 16370e747d08ec33070fc039d9ee2b6dde033cc8

Author: aobo-y

captum/_utils/common.py

@@ -175,9 +175,10 @@ def _format_tensor_into_tuples(
     if inputs is None:
         return None
     if not isinstance(inputs, tuple):
-        assert isinstance(
-            inputs, torch.Tensor
-        ), "`inputs` must have type " "torch.Tensor but {} found: ".format(type(inputs))
+        assert isinstance(inputs, torch.Tensor), (
+            "`inputs` must be a torch.Tensor or a tuple[torch.Tensor] "
+            f"but found: {type(inputs)}"
+        )
         inputs = (inputs,)
     return inputs