added missing docstring
added missing docstring


Former-commit-id: fd051289dfd76c750b285ebd34607d345773633f [formerly 38fc4603e478a7be9188d82cd75de5256cc8f410] [formerly 38fc4603e478a7be9188d82cd75de5256cc8f410 [formerly e8450e9e18bcc80909c2a768f2d61e629a3fa84a]]
Former-commit-id: bdb223afc908c3e2505ceb7559539e8c70854620
Former-commit-id: 0770cc59193c07b2d2d4f9779ec1ba6c194b5f1b
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine