    def from_dag(col_name: str, iter_type: str, inputs_type: List = None):
        """Return a SchemaRepr from the dag info.

        Args:
            col_name (`str`): Schema name.
            iter_type (`Dict[str, Any]`): The iteration type of this node.
            inputs_type (`List`): A list of the inputs schema type.

        Returns:
            SchemaRepr object.
        """
        if iter_type in [FlatMapConst.name, WindowConst.name, TimeWindowConst.name]:
            col_type = ColumnType.QUEUE
        elif iter_type == ConcatConst.name:
            col_type = inputs_type[0]
        elif iter_type in [WindowAllConst.name, ReduceConst.name]:
            col_type = ColumnType.SCALAR
        elif iter_type in [MapConst.name, FilterConst.name]:
            if inputs_type is not None and ColumnType.QUEUE in inputs_type:
                col_type = ColumnType.QUEUE
            else:
                col_type = ColumnType.SCALAR
        else:
            raise ValueError(f'Unknown iteration type: {iter_type}')
        return SchemaRepr(name=col_name, type=col_type)
Return a SchemaRepr from the dag info.

Args:
col_name (`str`): Schema name.
iter_type (`Dict[str, Any]`): The iteration type of this node.
inputs_type (`List`): A list of the inputs schema type.

Returns:
SchemaRepr object.
towhee/runtime/schema_repr.py