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 spel(isa, with_axis=False, ax=0):
    """plot super elements of I7/ISA7 model
    Args:
      isa: Isa7 object
    """
    from matplotlib.patches import Polygon
    if ax == 0:
        ax = plt.gca()
    ax.set_aspect('equal')
    for se in isa.superelements:
        ax.add_patch(Polygon([n.xy
                              for nc in se.nodechains
                              for n in nc.nodes],
                             color=isa.color[se.color], lw=0))

    ax.autoscale(enable=True)
    if not with_axis:
        ax.axis('off')