def METHOD_NAME(kappa, grid_spacing):
    """Lensing potential :math:`\\psi ({\\vec {\\theta }})` on the convergence grid
    :math:`\\kappa`.
    .. math::
        \\psi ({\\vec {\\theta }})={\\frac {1}{\\pi }}\\int d^{2}\\theta ^{\\prime }
        \\kappa ({\\vec {\\theta }}^{\\prime })\\ln |{\\vec {\\theta }}-{\\vec {\\theta }}^{\\prime }|
    The computation is performed as a convolution of the Green's function with the convergence map using FFT.
    :param kappa: 2d grid of convergence values
    :param grid_spacing: scale of an individual pixel (per axis) of grid
    :return: lensing potential in a 2d grid at positions x_grid, y_grid
    """
    num_pix = len(kappa) * 2
    if num_pix % 2 == 0:
        num_pix += 1
    kernel = potential_kernel(num_pix, grid_spacing)
    f_ = scp.fftconvolve(kappa, kernel, mode="same") / np.pi * grid_spacing**2
    return f_