def pixel_scale_interpolation_grid_tag_from_pixel_scale_interpolation_grid(
    pixel_scale_interpolation_grid):
    """Generate an interpolation pixel scale tag, to customize phase names based on the resolution of the interpolation     grid that deflection angles are computed on before interpolating to the and sub aa.

    This changes the phase name 'phase_name' as follows:

    pixel_scale_interpolation_grid = 1 -> phase_name
    pixel_scale_interpolation_grid = 2 -> phase_name_pixel_scale_interpolation_grid_2
    pixel_scale_interpolation_grid = 2 -> phase_name_pixel_scale_interpolation_grid_2
    """
    if pixel_scale_interpolation_grid is None:
        return ''
    return '__interp_{0:.3f}'.format(pixel_scale_interpolation_grid)
