As reported in https://github.com/mongodb-labs/mongo-arrow/issues/284#issuecomment-2724806018, with an accompanying PR in https://github.com/mongodb-labs/mongo-arrow/pull/285

The current implementation of pymongoarrow/schemas.py assings a projection of 'True' to all fields in a struct.
This does not work for structs that contain list-of-struct datatypes; this can be fixed by reworking the projection creation to use Mongo's dot notation.

Example:
read in a data field like
"a": {
"b": {
"c": [
{
"event":

,
"value": 2,
}
],
}
}

the projection to read this with a schema needs to be

The current implementation of the projection returns a projection of
{"a": {"b": {"c":

}}, which fails as the Mongo client reads "b" as an operator.