code: def add_reference_context_args(parser):
      
      reference_context_group = parser.add_argument_group("Reference Transcripts")
      parser.add_argument(
          "--context-size",
          default=CDNA_CONTEXT_SIZE,
          type=int)
      return reference_context_group
docs: Extends an ArgumentParser instance with the following commandline arguments:
          --context-size