public void EnterSequence()
{
_require(StreamOp.EnterSequence);
_reader.ReadOpenTag(_state.Tag);
var sequence = (SequenceSchema)_state.Schema;
var field = sequence.Fields[0];
_stack.Push(new SchemaState(sequence, _state.Tag, 0));
_state = new SchemaState(field.Type, field.Tag, -1);
}