Function verify_event 

pub fn verify_event(
    req: &EventRequest,
    resp: &EventResponse,
) -> Result<VerifiedEvent, VerifyError>

Verify an EventResponse against its EventRequest: req.at selects head (None) or leaf k, so a head response is never accepted for a positional request or vice versa. On Ok, resp.payload is verified. The public entry for event reads.