db/fields:
db/fields:

Fixed a semantic error: instance -> isinstance


Former-commit-id: cf697115444216babaa5e6251f67a188edc11f75 [formerly ddc7e51378137c50668bfc0e2e0726742efd2f7d]
Former-commit-id: d907ab2434bf3e01ee88f8bfa5a60b1899c34823
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine