code: def to_string_with_default(value, default_value):
          
          result = StringConverter.to_nullable_string(value)
          return result if result != None else default_value
docs: Converts value into string or returns default when value is None.
  
          :param value: the value to convert.
  
          :param default_value: the default value.
  
          :return: string value or default when value is null.