def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def testName(self):
        plotter = VoltageProfilePlotter(xaxis="frac_x")
        plotter.add_electrode(self.ie_LTO, "LTO insertion")
        plotter.add_electrode(self.ce_FF, "FeF3 conversion")
        self.assertIsNotNone(plotter.get_plot_data(self.ie_LTO))
        self.assertIsNotNone(plotter.get_plot_data(self.ce_FF))