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 _expandsubinclude(kindpats, root):
    """Returns the list of subinclude matcher args and the kindpats without the
    subincludes in it."""
    relmatchers = []
    other = []

    for kind, pat, source in kindpats:
        if kind == "subinclude":
            sourceroot = pathutil.dirname(util.normpath(source))
            pat = util.pconvert(pat)
            path = pathutil.join(sourceroot, pat)

            newroot = pathutil.dirname(path)
            matcherargs = (newroot, "", [], ["include:%s" % path])

            prefix = pathutil.canonpath(root, root, newroot)
            if prefix:
                prefix += "/"
            relmatchers.append((prefix, matcherargs))
        else:
            other.append((kind, pat, source))

    return relmatchers, other