Expand docstring for 'payload' / 'from_api_repr' to indicate polymorphism.

Addresses:
#1569 (comment)
#1569 (comment)

Author: tseaver

gcloud/logging/entries.py

@@ -21,8 +21,9 @@
 class _BaseEntry(object):
     """Base class for TextEntry, StructEntry.
 
-    :type payload: text
-    :param payload: The payload passed as ``textPayload``.
+    :type payload: text or dict
+    :param payload: The payload passed as ``textPayload``, ``jsonPayload``,
+                    or ``protoPayload``.
 
     :type logger: :class:`gcloud.logging.logger.Logger`
     :param logger: the logger used to write the entry.
@@ -41,7 +42,7 @@ def __init__(self, payload, logger, insert_id=None, timestamp=None):
 
     @classmethod
     def from_api_repr(cls, resource, client, loggers=None):
-        """Factory:  construct a text entry given its API representation
+        """Factory:  construct an entry given its API representation
 
         :type resource: dict
         :param resource: text entry resource representation returned from