code: def test_streamlines_generator():
      # Test generator
      streamlines_generator = Streamlines(generate_sl(streamlines))
      npt.assert_equal(len(streamlines_generator), len(streamlines))
      # Nothing should change
      streamlines_generator.append(np.array([]))
      npt.assert_equal(len(streamlines_generator), len(streamlines))
  
      # Test append error
      npt.assert_raises(
          ValueError,
          streamlines_generator.append,
          np.array(streamlines, dtype=object),
      )
  
      # Test empty streamlines
      streamlines_generator = Streamlines(np.array([]))
      npt.assert_equal(len(streamlines_generator), 0)
  
imports: import warnings
  import types
  import numpy
  from numpy.linalg import norm
  import numpy.testing
  from dipy.testing.memory import get_type_refcount
  from dipy.testing import assert_arrays_equal
  from dipy.testing.decorators import set_random_number_generator
  from dipy.testing import assert_true
  from numpy.testing import assert_array_equal, assert_array_almost_equal, assert_raises, assert_allclose, assert_almost_equal, assert_equal
  from dipy.tracking.streamlinespeed import compress_streamlines, length, set_number_of_points
  from dipy.tracking.streamline import Streamlines
  from dipy.tracking.streamline import relist_streamlines, unlist_streamlines, center_streamlines, transform_streamlines, select_random_set_of_streamlines, select_by_rois, orient_by_rois, orient_by_streamline, values_from_volume, deform_streamlines, cluster_confidence
label_desc: Use image node_id 23 for calling a global function with example usage: test_streamlines_generator() without return types