Return warnings if some method parameters are invalid or otherwise ignored

[hthomas-czi]

Visibility of system status is an important usability heuristic. We should communicate to users if the system deviates from their intention.

User Quote

if filtering with a cell type ontology label that was not present in the census, the query completes, but it silently drops the missing ontology terms. This should be verbose so that the user knows which terms were dropped.

[ebezzi]

This request is unclear. The users can check the existence of such terms themselves (e.g. by checking either the categories or unique values for an obs column) before issuing the query. Doing this static check as part of the API will incur into a performance hit and is not how the vast majority of the query systems work (including SQL).