class_docstr: SchemaRepr test
code: def test_raise(self):
      with self.assertRaises(ValueError):
          SchemaRepr.from_dag("a", "flat_maps", [ColumnType.QUEUE])
  
file_path: towhee/tests/unittests/runtime/test_schema_repr.py
imports: import unittest
  from towhee.runtime.schema_repr import SchemaRepr
  from towhee.runtime.data_queue import ColumnType
label_desc: Use image node_id 4 for calling the TestSchemaRepr obj's underlying member method code with example usage: obj.test_raise() without return types