def scan(self, search_path=None):
        """Scan `search_path` for distributions usable in this environment

        Any distributions found are added to the environment.
        `search_path` should be a sequence of ``sys.path`` items.  If not
        supplied, ``sys.path`` is used.  Only distributions conforming to
        the platform/python version defined at initialization are added.
        """
        if search_path is None:
            search_path = sys.path

        for item in search_path:
            for dist in find_distributions(item):
                self.add(dist)
Scan `search_path` for distributions usable in this environment

        Any distributions found are added to the environment.
        `search_path` should be a sequence of ``sys.path`` items.  If not
        supplied, ``sys.path`` is used.  Only distributions conforming to
        the platform/python version defined at initialization are added.
        
src/pkg_resources/__init__.py