!5683 Address with 'param not None' case

Merge pull request !5683 from peixu_ren/custom_bijector

mindspore/nn/probability/bijector/bijector.py

@@ -50,6 +50,8 @@ class Bijector(Cell):
         self._parameters = {}
         # parsing parameters
         for k in param.keys():
+            if k == 'param':
+                continue
             if not(k == 'self' or k.startswith('_')):
                 self._parameters[k] = param[k]
         self._is_constant_jacobian = is_constant_jacobian

mindspore/nn/probability/bijector/power_transform.py

@@ -35,6 +35,9 @@ class PowerTransform(Bijector):
     Args:
         power (int or float): scale factor. Default: 0.
         name (str): name of the bijector. Default: 'PowerTransform'.
+        param (dict): parameters used to initialize the bijector. This is only used when other bijectors that inherits
+          from powertransform passing in parameters. In this case the derived bijector may overwrite the param args.
+          Default: None.
 
     Examples:
         >>> # To initialize a PowerTransform bijector of power 0.5