code: def _get_national_number_groups_without_pattern(numobj):
      
      # This will be in the format +CC-DG1-DG2-DGX;ext=EXT where DG1..DGX represents groups of
      # digits.
      rfc3966_format = format_number(numobj, PhoneNumberFormat.RFC3966)
      # We remove the extension part from the formatted string before splitting
      # it into different groups.
      end_index = rfc3966_format.find(U_SEMICOLON)
      if end_index < 0:
          end_index = len(rfc3966_format)
  
      # The country-code will have a '-' following it.
      start_index = rfc3966_format.find(U_DASH) + 1
      return rfc3966_format[start_index:end_index].split(U_DASH)
docs: Helper method to get the national-number part of a number, formatted without any national
      prefix, and return it as a set of digit blocks that would be formatted together following
      standard formatting rules.