class_docstr: Unit tests for the nearest neighbors builder class.
code: def create_builder(self, default_class_label="default_label"):
      builder = KNearestNeighborsClassifierBuilder(
          input_name="input",
          output_name="output",
          number_of_dimensions=4,
          default_class_label=default_class_label,
      )
      return builder
  
imports: import os
  import shutil
  import unittest
  from coremltools._deps import _HAS_SKLEARN
  from coremltools.models import MLModel
  from coremltools.models.nearest_neighbors import KNearestNeighborsClassifierBuilder
  from coremltools.models.utils import _is_macos
label_desc: Use image node_id 3 for calling the NearestNeighborsBuilderTest obj's underlying member method code with example usage: obj.create_builder(default_class_label) and returns: builder