def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
def __init__(self, root, cwd, kindpats, ctx=None, badfn=None):
        super(patternmatcher, self).__init__(root, cwd, badfn)
        # kindpats are already normalized to be relative to repo-root.
        # Can we use tree matcher?
        rules = _kindpatstoglobs(kindpats, recursive=False)
        fallback = True
        if rules is not None:
            try:
                matcher = treematcher(root, cwd, badfn=badfn, rules=rules)
                # Replace self to 'matcher'.
                self.__dict__ = matcher.__dict__
                self.__class__ = matcher.__class__
                fallback = False
            except ValueError:
                # for example, Regex("Compiled regex exceeds size limit of 10485760 bytes.")
                pass
        if fallback:
            self._prefix = _prefix(kindpats)
            self._pats, self.matchfn = _buildmatch(ctx, kindpats, "$", root)

        self._files = _explicitfiles(kindpats)