'Gets Course or Library by locator'

def _get_structure(self, structure_id, depth, head_validation=True, **kwargs):

    structure_entry = self._lookup_course(structure_id, head_validation=head_validation)
    root = structure_entry.structure['root']
    result = self._load_items(structure_entry, [root], depth, **kwargs)
    return result[0]
