code: def func(x):
      return x[0] ** 2 + x[1] ** 2 + x[2] ** 2
  
file_path: dipy/dipy/core/tests/test_optimize.py
imports: import numpy
  import scipy.sparse
  import numpy.testing
  from dipy.core.optimize import Optimizer, sparse_nnls, spdot
  import dipy.core.optimize
  from dipy.testing.decorators import set_random_number_generator
label_desc: Use image node_id 1 for calling a global function with example usage: func(x) and returns: unknown