message: Update comments in struct.proto to match commit
diff: @@ -137,16 +137,20 @@ message TypeSpecProto {
  VARIABLE_SPEC = 9; // tf.VariableSpec
  ROW_PARTITION_SPEC = 10; // RowPartitionSpec from ragged/row_partition.py
  reserved 11;
  - REGISTERED_TYPE_SPEC = 12;
  + REGISTERED_TYPE_SPEC = 12; // The type registered as type_spec_class_name.
  }
  TypeSpecClass type_spec_class = 1;
  // The value returned by TypeSpec._serialize().
  StructuredValue type_state = 2;
  - // This is currently redundant with the type_spec_class enum, and is only
  - // used for error reporting. In particular, if you use an older binary to
  - // load a newer model, and the model uses a TypeSpecClass that the older
  - // binary doesn't support, then this lets us display a useful error message.
  + // The name of the TypeSpec class.
  + // * If type_spec_class == REGISTERED_TYPE_SPEC, the TypeSpec class is
  + // the one registered under this name. For types registered outside
  + // core TensorFlow by an add-on library, that library must be loaded
  + // before this value can be deserialized by StructureCoder.
  + // * If type_spec_class specifies a particular TypeSpec class, this field is
  + // redundant with the type_spec_class enum, and is only used for error
  + // reporting in older binaries that do not know the tupe_spec_class enum.
  string type_spec_class_name = 3;
  }
  