INVALID_OBSERVED_METRICS error class
Invalid observed metrics.
Aggregate expressions with DISTINCT are not allowed in observed metrics, but found: <expr>.
Aggregate expression with FILTER predicate are not allowed in observed metrics, but found: <expr>.
The observed metrics should be named: <operator>.
Nested aggregates are not allowed in observed metrics, but found: <expr>.
Attribute <expr> can only be used as an argument to an aggregate function.
Non-deterministic expression <expr> can only be used as an argument to an aggregate function.
Window expressions are not allowed in observed metrics, but found: <expr>.