def column(self, name: str) -> Column:
        """Returns Column instance with a type if name is found in current schema,
        otherwise raises an exception.
        """
        if "." in name:
            name_path = name.split(".")
        elif DEFAULT_DELIMITER in name:
            name_path = name.split(DEFAULT_DELIMITER)
        else:
            name_path = [name]
        for path, type_, _, _ in self.signals_schema.get_flat_tree():
            if path == name_path:
                return Column(name, python_to_sql(type_))

        raise ValueError(f"Column with name {name} not found in the schema")
Returns Column instance with a type if name is found in current schema,
        otherwise raises an exception.
        
src/datachain/lib/dc/datachain.py