"Point reflection" or "point symmetry" is a basic concept in geometry where a given point, P, at a given position relative to a mid-point, Q has a corresponding point, P1, which is the same distance from Q but in the opposite direction.
## Task
Given two points P and Q, output the symmetric point of point P about Q.
Each argument is a two-element array of integers representing the point's X and Y coordinates.  Output should be in the same format, giving the X and Y coordinates of point P1.  You do not have to validate the input.
This kata was inspired by the Hackerrank challenge [Find Point](https://www.hackerrank.com/challenges/find-point)
def symmetric_point(p, q):
    p2_x = p[0]+2*(q[0]-p[0])
    p2_y = p[1]+2*(q[1]-p[1])
    return [p2_x, p2_y]
def symmetric_point(p, q):
    p2_x = p[0]+2*(q[0]-p[0])
    p2_y = p[1]+2*(q[1]-p[1])
    return [p2_x, p2_y]