:param x:                   The first element of a possible match.
    :param y:                   The second element of a possible match.
    :param matched_a:           The current matches for the first set.
    :param matched_b:           The current matches for the second set.
    :param attributes_dict_a:   The attributes for each element in the first set.
    :param attributes_dict_b:   The attributes for each element in the second set.
    :returns:                   True/False

def _is_better_match(x, y, matched_a, matched_b, attributes_dict_a, attributes_dict_b):
    """
    :param x:                   The first element of a possible match.
    :param y:                   The second element of a possible match.
    :param matched_a:           The current matches for the first set.
    :param matched_b:           The current matches for the second set.
    :param attributes_dict_a:   The attributes for each element in the first set.
    :param attributes_dict_b:   The attributes for each element in the second set.
    :returns:                   True/False
    """
    attributes_x = attributes_dict_a[x]
    attributes_y = attributes_dict_b[y]
    if x in matched_a:
        attributes_match = attributes_dict_b[matched_a[x]]
        if _euclidean_dist(attributes_x, attributes_y) >= _euclidean_dist(attributes_x, attributes_match):
            return False
    if y in matched_b:
        attributes_match = attributes_dict_a[matched_b[y]]
        if _euclidean_dist(attributes_x, attributes_y) >= _euclidean_dist(attributes_y, attributes_match):
            return False
    return True