!7093 Add description of seed that TransformedDistribution uses

Merge pull request !7093 from peixu_ren/master

mindspore/nn/probability/distribution/transformed_distribution.py

@@ -32,6 +32,8 @@ class TransformedDistribution(Distribution):
         bijector (Bijector): The transformation to perform.
         distribution (Distribution): The original distribution.
         seed (int): The seed is used in sampling. The global seed is used if it is None.
+          If this seed is given when a TransformedDistribution object is initialised, the object's sampling function
+          will use this seed; elsewise, the underlying distribution's seed will be used.
         name (str): The name of the transformed distribution. Default: 'transformed_distribution'.
 
     Note: