code: def n_classes():
      return 10
  
imports: import numpy
  import pytest
  from thinc.api import Adam, ArgsKwargs, Linear, Model, TensorFlowWrapper, get_current_ops, keras_subclass, tensorflow2xp, xp2tensorflow
  from thinc.compat import has_cupy_gpu, has_tensorflow
  from thinc.util import to_categorical
  from ..util import check_input_converters, make_tempdir
label_desc: Use image node_id 3 for calling a global function with example usage: n_classes() and returns: int