code: def convergence_from_grid(self, grid):
          
  
          surface_density_grid = np.zeros(grid.shape[0])
  
          grid_eta = self.grid_to_elliptical_radii(grid)
  
          for i in range(grid.shape[0]):
              surface_density_grid[i] = self.convergence_func(grid_eta[i])
  
          return surface_density_grid
docs: Calculate the projected convergence at a given set of arc-second gridded coordinates.
  
          Parameters
          ----------
          grid : grids.RegularGrid
              The grid of (y,x) arc-second coordinates the surface density is computed on.