code: def safe_display_name(numobj, lang, script=None, region=None):
      
      if is_mobile_number_portable_region(region_code_for_number(numobj)):
          return U_EMPTY_STRING
      return name_for_number(numobj, lang, script, region)
docs: Gets the name of the carrier for the given PhoneNumber object only when
      it is 'safe' to display to users.  A carrier name is onsidered safe if the
      number is valid and for a region that doesn't support mobile number
      portability (http://en.wikipedia.org/wiki/Mobile_number_portability).
  
  
      This function explicitly checks the validity of the number passed in
  
      Arguments:
      numobj -- The PhoneNumber object for which we want to get a carrier name.
      lang -- A 2-letter lowercase ISO 639-1 language code for the language in
                    which the description should be returned (e.g. "en")
      script -- A 4-letter titlecase (first letter uppercase, rest lowercase)
                    ISO script code as defined in ISO 15924, separated by an
                    underscore (e.g. "Hant")
      region --  A 2-letter uppercase ISO 3166-1 country code (e.g. "GB")
  
      Returns a carrier name that is safe to display to users, or the empty string.