code: def linear_model(x, y):
          
          x1, x2 = x
          y1, y2 = y
          m = (y2 - y1) / (x2 - x1)
          b = y1 - (m * x1)
          return lambda x: m * x + b
docs: Returns a linear model transformation function fitted on the two supplied points.
          y = m*x + b
          Note: Assumes that slope > 0, otherwise division through zero might occur.