input: Write a function to calculate the distance between two points on a two-dimensional plane. The function should take four arguments, x1, y1, x2, and y2, representing the coordinates of the two points, and return the distance as a float.
  
  assert calculate_distance(3, 4, -9, -2) == 13.60147
  assert calculate_distance(0, 0, 0, 0) == 0.0
  assert calculate_distance(1, 2, 4, 6) == 5.0
  assert calculate_distance(-1, -1, 1, 1) == 2.828427
output: def calculate_distance(x1, y1, x2, y2):
      return ((x2 - x1) ** 2 + (y2 - y1) ** 2) ** 0.5