def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def testPlotly(self):
        plotter = VoltageProfilePlotter(xaxis="frac_x")
        plotter.add_electrode(self.ie_LTO, "LTO insertion")
        plotter.add_electrode(self.ce_FF, "FeF3 conversion")
        fig = plotter.get_plotly_figure()
        self.assertEqual(fig.layout.xaxis.title.text, "Atomic Fraction of Li")
        plotter = VoltageProfilePlotter(xaxis="x_form")
        plotter.add_electrode(self.ce_FF, "FeF3 conversion")
        fig = plotter.get_plotly_figure()
        self.assertEqual(fig.layout.xaxis.title.text, "x in Li<sub>x</sub>FeF3")

        plotter.add_electrode(self.ie_LTO, "LTO insertion")
        fig = plotter.get_plotly_figure()
        self.assertEqual(fig.layout.xaxis.title.text, "x Workion Ion per Host F.U.")