docs: def distance(x0, x1, y0, y1):
      """
      Function that calculates the square of the distance between two points.
  
  
      Parameters
      -----
          x0:  x - coordinate of point 0
          x1:  x - coordinate of point 1
          y0:  y - coordinate of point 0
          y1:  y - coordinate of point 1
  
  
      Returns
      ------
          distance : float
          square of distance 
            
      """   
      # Calculate square of the distance between two points (Pythagoras)
      distance = (x1.values- x0.values)*(x1.values- x0.values)\
          + (y1.values- y0.values)*(y1.values- y0.values)
      return distance