added missing docstring
added missing docstring


Former-commit-id: c05948a2fc94300ff40d1194dd1831b520fe328a [formerly c05948a2fc94300ff40d1194dd1831b520fe328a [formerly 65eb8e6809175598d9885958566efd573332cca0]]
Former-commit-id: cb7b410415dc514eb519287fab7c277d0019f2c3
Former-commit-id: 735b4945b7d6f8da52428dc7496b42ca46f5117b
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine