input: Write a function to calculate the Euclidean distance between two points in a 2D plane. The function should take four arguments corresponding to the x and y coordinates of the two points. It should return the distance as a float. If the points are identical, it should return 0.
  assert distance_between_points(2, 7, 4, 9) == 2.8284271247461903
  assert distance_between_points(0, 0, 0, 0) == 0
  assert distance_between_points(-1, -1, 1, 1) == 2.8284271247461903
  assert distance_between_points(3, 4, 7, 1) == 5.0
  assert distance_between_points(1, 2, 5, 5) == 5.0
output: def distance_between_points(x1, y1, x2, y2):
      return ((x2 - x1) ** 2 + (y2 - y1) ** 2) ** 0.5