input: Write a function to calculate the distance between two points given their coordinates (x1, y1) and (x2, y2). 
  assert distance_between_points(2, 7, 4, 9) == math.sqrt(8)
  assert distance_between_points(0, 0, 0, 0) == 0
  assert distance_between_points(1, 1, 4, 5) == 5
  assert distance_between_points(-2, -3, 1, 1) == 5
  assert distance_between_points(3, 4, 7, 1) == 5
output: import math
  
  def distance_between_points(x1, y1, x2, y2):
      return math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)