code: def test_variable_shape(self, DenseLayer):
      # should work:
      assert DenseLayer((None, 10), 20).output_shape == (None, 20)
      assert DenseLayer(
          (10, None, 10), 20, num_leading_axes=2
      ).output_shape == (10, None, 20)
      # should fail:
      for shape, num_leading_axes in ((10, None), 1), (
          (10, None, 10),
          1,
      ):
          with pytest.raises(ValueError) as exc:
              DenseLayer(shape, 20, num_leading_axes=num_leading_axes)
          assert "requires a fixed input shape" in exc.value.args[0]
  
imports: from mock import Mock
  import numpy
  import pytest
  import theano
  import lasagne
label_desc: Use image node_id 7 for calling the TestDenseLayer obj's underlying member method code with example usage: obj.test_variable_shape(DenseLayer) without return types