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 mesh(isa, with_axis=False, ax=0):
    """plot mesh of I7/ISA7 model
    Args:
      isa: Isa7 object
    """
    from matplotlib.lines import Line2D
    if ax == 0:
        ax = plt.gca()
    ax.set_aspect('equal')
    for el in isa.elements:
        pts = [list(i) for i in zip(*[v.xy for v in el.vertices])]
        ax.add_line(Line2D(pts[0], pts[1], color='b', ls='-', lw=0.25))

    # for nc in isa.nodechains:
    #    pts = [list(i) for i in zip(*[(n.x, n.y) for n in nc.nodes])]
    #    ax.add_line(Line2D(pts[0], pts[1], color="b", ls="-", lw=0.25,
    #                       marker=".", ms="2", mec="None"))

    # for nc in isa.nodechains:
    #    if nc.nodemid is not None:
    #        plt.plot(*nc.nodemid.xy, "rx")

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