def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def git_checkout(git_url, git_branch=None, git_tag=None, git_hash=None):
    git_dst = tempfile.mkdtemp()
    g = GitManager(url=git_url, git_dst=git_dst, git_branch=git_branch, git_tag=git_tag, git_hash=git_hash)
    g.run()
    shutil.rmtree(git_dst)