Function execute 

pub async fn execute<S: StorageBackend>(
    storage: &S,
    stmt: &Statement,
    parameters: &[AttributeValue],
    limit: Option<usize>,
) -> Result<Option<Vec<Item>>>

Execute a parsed PartiQL statement.

Returns Some(items) for SELECT (may be empty), None for write operations. An optional limit restricts how many items a SELECT returns.