def contraint_is_price_ratio_type(bounds_key):
    """ Checks if given parameter is a tuple with two elements. In the case of price
        ratio weight restrictions key of bounds dictionary will be a tuple with two
        elements.

        Args:
            tuple of str: tuple with elements.

        Returns:
            bool: true if given element is a tuple with two elements, false otherwise.
    """
    return isinstance(bounds_key, tuple) and len(bounds_key) == 2
