Modified the generator output for get_annual_occurrence_rates of MultiMFD
Modified the generator output for get_annual_occurrence_rates of MultiMFD


Former-commit-id: a1370fd1943ab7e72f637bbd2cc25b22e0bc211a
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine