Merge pull request #722 from srini100/docfix

Add note about pb2 naming in Python.

Author: hsaliak

docs/tutorials/basic/python.md

@@ -185,6 +185,8 @@ than creates a new one. The generated code files are called
    - `add_RouteGuideServicer_to_server`, which adds a RouteGuideServicer to
      a `grpc.Server`
 
+Note: The `2` in pb2 indicates that the generated code is following Protocol Buffers Python API version 2. Version 1 is obsolete. It has no relation to the Protocol Buffers Language version, which is the one indicated by `syntax = "proto3"` or `syntax = "proto2"` in a .proto file.
+
 <a name="server"></a>
 
 ## Creating the server