A protocol buffer message, instance of Message,
or a protocol message descriptor, instance of Descriptor
...
ignored
Value
For messages, a list of the content of the fields is
returned.For message type descriptors, a list containing
nested type descriptors (Descriptor objects),
enum type descriptors (EnumDescriptor objects),
then field descriptors (FieldDescriptor objects) in that order.For enum descriptors, a named list of the enumerated values.For file descriptors, a named list of descriptors defined in the
specified file descriptor.For service descriptors, ...