code: def function(x, y, amp, a_x, a_y, center_x, center_y):
      
      x_shift = x - center_x
      y_shift = y - center_y
      A = np.pi * a_x * a_y
      dist = (x_shift/a_x)**2 + (y_shift/a_y)**2
      torus = np.zeros_like(x)
      torus[dist <= 1] = 1
      return amp/A * torus
docs: returns torus (ellipse with constant surface brightnes) profile