Sets the uncertainty *value* for an uncertainty *name*. *value* should have one of the
        formats as described in :py:meth:`uncertainties`.

def set_uncertainty(self, name, value):
        """
        Sets the uncertainty *value* for an uncertainty *name*. *value* should have one of the
        formats as described in :py:meth:`uncertainties`.
        """
        uncertainties = self.__class__.uncertainties.fparse(self, {name: value})
        self._uncertainties.update(uncertainties)