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