Added comments
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Former-commit-id: ac46036e4c07d24398383dc211d8bf2f07497025 [formerly 7ed179629bfd8950bf0562500effa01d74be2c6f]
Former-commit-id: 27783a6f5b402dba39db4d0b44e5030e914251a1
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine