ProtoSchema describes the schema of the serialized protocol
buffer data rows.
Attribute
Name
Description
proto_descriptor
google.protobuf.descriptor_pb2.DescriptorProto
Descriptor for input message. The descriptor
has to be self contained, including all the
nested types, excepted for proto buffer well
known types
(https://developers.google.com/protocol-buffers/docs/reference/google.protobuf).