input: Write a function to calculate the distance between two points in a 2D plane using their coordinates. If the given coordinates are invalid, return -1.
  assert distance_between_points(2, 7, 4, 9)==2.8284271247461903
  assert distance_between_points(0, 0, 0, 0)==0
  assert distance_between_points(3, -4, -3, 4)==10
  assert distance_between_points(None, 7, 4, 9)==-1
  assert distance_between_points(2, 7, None, 9)==-1
output: def distance_between_points(x1, y1, x2, y2):
      if x1 is None or y1 is None or x2 is None or y2 is None:
          return -1
      return ((x2 - x1) ** 2 + (y2 - y1) ** 2) ** 0.5