Remove useless __len__ method
Remove useless __len__ method


Former-commit-id: eed9cebbbf1cc1ad9cc72072502268f2db2bd2f1 [formerly a8b89714e30ae6b796544d844b063b50e1204112] [formerly a8b89714e30ae6b796544d844b063b50e1204112 [formerly cb28a32baaccead13af86b393dc0557d25f5647e]]
Former-commit-id: 4d4e31c5472985877c12e96d9767dd93e67e1100
Former-commit-id: 0d230b35e5bf2d142954998da39741aed4bfb778
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine