Return the number of significant digits to %g-format *value*, assuming that
        it is known with an error of *delta*.
        """
        if delta == 0:
            if value == 0:
                # if both value and delta are 0, np.spacing below returns 5e-324
                # which results in rather silly results
                return 3
            # delta = 0 may occur when trying to format values over a tiny range;
            # in that case, replace it by the distance to the closest float.
>           delta = abs(np.spacing(value))
                        ^^^^^^^^^^^^^^^^^
E           RuntimeWarning: invalid value encountered in spacing

lib\matplotlib\cbook.py:2238: RuntimeWarning