code: def test_unknown_dtypes():
      op = MyOperand(_output_types=[OutputType.dataframe])
      df = op.new_tileable(None, dtypes=None)
      op2 = MyOperand(_output_types=[OutputType.scalar])
      with pytest.raises(ValueError) as exc_info:
          op2.new_tileable([df])
      assert "executed first" in exc_info.value.args[0]
  
imports: import numpy
  import pandas
  import pytest
  from ....dataframe import core
  from ...None import OutputType
  from ..None import Operand, TileableOperandMixin, execute, estimate_size, ShuffleProxy
label_desc: Use image node_id 3 for calling a global function with example usage: test_unknown_dtypes() without return types