def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
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.")