def requires(self, extras=()):
        """List of Requirements needed for this distro if `extras` are used"""
        dm = self._dep_map
        deps = []
        deps.extend(dm.get(None, ()))
        for ext in extras:
            try:
                deps.extend(dm[safe_extra(ext)])
            except __HOLE__:
                raise UnknownExtra(
                    "%s has no such extra feature %r" % (self, ext)
                )
        return deps
dataset/ETHPy150Open anzev/hedwig/build/pip/pip/_vendor/pkg_resources/__init__.py/Distribution.requires