code: def _add_strings_to_commastring(self, field, strings):
          # type: (str, List[str]) -> bool
          
          allstringsadded = True
          for string in strings:
              if not self._add_string_to_commastring(field, string):
                  allstringsadded = False
          return allstringsadded
docs: Add a list of strings to a comma separated list of strings
  
          Args:
              field (str): Field containing comma separated list
              strings (List[str]): list of strings to add
  
          Returns:
              bool: True if all strings added or False if any already present.