def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def __draw_ellipse(ax, x, y, angle, width, height, color):
        if (width > 0.0) and (height > 0.0):
            ax.plot(x, y, color=color, marker='x', markersize=6)
            ellipse = patches.Ellipse((x, y), width, height, alpha=0.2, angle=-angle, linewidth=2, fill=True, zorder=2, color=color)
            ax.add_patch(ellipse)