code: def _remove_string_from_commastring(self, field, string):
          # type: (str, str) -> bool
          
          commastring = self.data.get(field, '')
          if string in commastring:
              self.data[field] = commastring.replace(string, '')
              return True
          return False
docs: Remove a string from a comma separated list of strings
  
          Args:
              field (str): Field containing comma separated list
              string (str): String to remove
  
          Returns:
              bool: True if string removed or False if not