Update precision_plugin.py

Author: justusschock

pytorch_lightning/plugins/precision/precision_plugin.py

@@ -22,6 +22,9 @@
 
 
 class PrecisionPlugin(Plugin):
+    """ Plugin handling the precision-specific parts of the training.
+    The static classattributes EPSILON and precision must be overwritten in child-classes and their default values reflect fp32 training
+    """
     EPSILON = 1e-6
     precision = 32