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 _split_horizontal(container):
		r1 = None
		r2 = None
		min_h = int(H_RATIO*container.w)+1
		if container.h < 2*min_h:
			return None
		r1 = Container(container.x,container.y,container.w,randint(min_h, container.h-min_h))
		r2 = Container(container.x,container.y+r1.h,container.w,container.h-r1.h)
		return [r1, r2]