Generate a valid num_values string based off min_values and max_values
        :return: string

def _num_values(self):
        """
        Generate a valid num_values string based off min_values and max_values
        :return: string
        """
        # Add min_values to string
        num_values = str(self.min_values) if self.min_values else "0"

        # Handle infinite max_values or finite max_values
        if self.max_values is None or self.max_values == float("inf"):
            num_values += "+"
        else:
            num_values += ".." + str(self.max_values)

        # Return the num_values string
        return num_values