Is It a Parallelogram?

Given a list of four points in the plane, determine if they are the vertices of a parallelogram.

Examples

is_parallelogram([(0, 0), (1, 0), (1, 1), (0, 1)]) ➞ True

is_parallelogram([(0, 0), (2, 0), (1, 1), (0, 1)]) ➞ False

is_parallelogram([(0, 0), (1, 1), (1, 4), (0, 3)]) ➞ True

is_parallelogram([(0, 0), (1, 2), (2, 1), (3, 3)]) ➞ True

is_parallelogram([(0, 0), (1, 0), (0, 1), (1, 1)]) ➞ True

Notes

The points may be given in any order (compare examples #1 and #5).