code: def _extract_country_code(number):
      
  
      if len(number) == 0 or number[0] == U_ZERO:
          # Country codes do not begin with a '0'.
          return (0, number)
      for ii in range(1, min(len(number), _MAX_LENGTH_COUNTRY_CODE) + 1):
          try:
              country_code = int(number[:ii])
              if country_code in COUNTRY_CODE_TO_REGION_CODE:
                  return (country_code, number[ii:])
          except Exception:
              pass
      return (0, number)
docs: Extracts country calling code from number.
  
      Returns a 2-tuple of (country_calling_code, rest_of_number).  It assumes
      that the leading plus sign or IDD has already been removed.  Returns (0,
      number) if number doesn't start with a valid country calling code.