def fetch_scopes_for(self, atom_name):
        """Fetches a walker of the visible scopes for the given atom."""
        try:
            return self._fetch_atom_metadata_entry(atom_name, 'scope_walker')
        except __HOLE__:
            # This signals to the caller that there is no walker for whatever
            # atom name was given that doesn't really have any associated atom
            # known to be named with that name; this is done since the storage
            # layer will call into this layer to fetch a scope for a named
            # atom and users can provide random names that do not actually
            # exist...
            return None

    # Various helper methods used by the runtime components; not for public
    # consumption...
dataset/ETHPy150Open openstack/taskflow/taskflow/engines/action_engine/runtime.py/Runtime.fetch_scopes_for