String Field has three constraints (apart from anything
        in the super class)

        Args:
            field (StringField): actual string field object from a
            model declaration

        Returns:
            random string value

def make_string_field_value(cls, field):
        """
        String Field has three constraints (apart from anything
        in the super class)

        Args:
            field (StringField): actual string field object from a
            model declaration

        Returns:
            random string value
        """
        if field.regex is not None:
            raise NotImplementedError

        string_range = cls.get_range(field)

        return cls.get_random_string(string_range)