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 i1beta_torque(i1, beta, torque, title='', ax=0):
    """creates a surface plot of torque vs i1, beta"""
    if ax == 0:
        _create_3d_axis()
        ax = plt.gca()
    azim = 210
    if 0 < np.mean(beta) or -90 > np.mean(beta):
        azim = -60
    unit = 'Nm'
    scale = 1
    if np.min(torque) < -9.9e3 or np.max(torque) > 9.9e3:
        scale = 1e-3
        unit = 'kNm'
    if title:
        _plot_surface(ax, i1, beta, scale*np.asarray(torque),
                      (u'I1/A', u'Beta/°', title),
                      azim=azim)
    else:
        _plot_surface(ax, i1, beta, scale*np.asarray(torque),
                      (u'I1/A', u'Beta/°', u'Torque/{}'.format(unit)),
                      azim=azim)