input: Write a python function to calculate the distance between two points.
  assert calculate_distance(0, 0, 3, 4) == 5.0
  assert calculate_distance(1, 1, 4, 5) == 5.0
  assert calculate_distance(-1, -1, -4, -5) == 5.0
output: def calculate_distance(x1, y1, x2, y2):
      return ((x2 - x1)**2 + (y2 - y1)**2)**0.5