code: def grid_to_grid_radii(self, grid):
          
          return np.sqrt(np.add(np.square(grid[:, 0]), np.square(grid[:, 1])))
docs: Convert a grid of (y, x) coordinates to a grid of their circular radii.
  
          If the coordinates have not been transformed to the profile's centre, this is performed automatically.
  
          Parameters
          ----------
          grid : TransformedGrid(ndarray)
              The (y, x) coordinates in the reference frame of the profile.