code: def ndd_prefix_for_region(region_code, strip_non_digits):
      
      if region_code is None:
          return None
      metadata = PhoneMetadata.metadata_for_region(region_code.upper(), None)
      if metadata is None:
          return None
      national_prefix = metadata.national_prefix
      if national_prefix is None or len(national_prefix) == 0:
          return None
      if strip_non_digits:
          # Note: if any other non-numeric symbols are ever used in national
          # prefixes, these would have to be removed here as well.
          national_prefix = re.sub(U_TILDE, U_EMPTY_STRING, national_prefix)
      return national_prefix
docs: Returns the national dialling prefix for a specific region.
  
      For example, this would be 1 for the United States, and 0 for New
      Zealand. Set strip_non_digits to True to strip symbols like "~" (which
      indicates a wait for a dialling tone) from the prefix returned. If no
      national prefix is present, we return None.
  
      Warning: Do not use this method for do-your-own formatting - for some
      regions, the national dialling prefix is used only for certain types of
      numbers. Use the library's formatting functions to prefix the national
      prefix when required.
  
      Arguments:
      region_code -- The region that we want to get the dialling prefix for.
      strip_non_digits -- whether to strip non-digits from the national
                 dialling prefix.
  
      Returns the dialling prefix for the region denoted by region_code.