code: def fill_parser(self, subparser):
      subparser.add_argument(
          "doctype",
          nargs="*",
          help=f"the document types to be associated with the notebook editor; "
          f"defaults to {' '.join(LabConfig.DOCTYPES)}",
      )
  
imports: import sys
  from argparse import ArgumentParser
  from pathlib import Path
  import jupyter_core.paths
  from .labconfig import LabConfig
label_desc: Use image node_id 3 for calling the SetDefaultViewer obj's underlying member method code with example usage: obj.fill_parser(subparser) without return types