def METHOD_NAME():
    grid = make_pupil_grid(2)
    A = Field(np.random.randn(3, 3, grid.size), grid)
    B = field_inv(A)
    BB = np.empty_like(B)
    for i in range(grid.size):
        BB[..., i] = np.linalg.inv(A[..., i])
    assert np.allclose(B, BB)