Function verify 

pub fn verify<Mode: ExecutionMode>(
    env: &Env<'_, '_, '_, '_, '_, Mode>,
    txn: &Transaction,
) -> Result<(), Mode::Error>

Checks the following

• valid visibility for move function calls
  • Can be disabled under certain execution modes
• private generics rules for move function calls
• no references returned from move calls
  • Can be disabled under certain execution modes
  • Can be disabled via a feature flag