docs: def read_metadata(text, ext):
      """Return the header metadata"""
      ext = '.' + ext.split('.')[-1]
      lines = text.splitlines()
  
      if ext in ['.md', '.Rmd']:
          comment = ''
      else:
          comment = _SCRIPT_EXTENSIONS.get(ext, {}).get('comment', '#')
  
      metadata, _, _, _ = header_to_metadata_and_cell(lines, comment, ext)
      if ext in ['.r', '.R'] and not metadata:
          metadata, _, _, _ = header_to_metadata_and_cell(lines, "#'", ext)
  
      return metadata