code: def z_only(z):
      cosz = np.cos(z)
      sinz = np.sin(z)
      return np.array(
          [
              [cosz, -sinz, 0],
              [sinz, cosz, 0],
              [0, 0, 1],
          ]
      )
  
file_path: nibabel/nibabel/tests/test_euler.py
imports: import math
  import numpy
  import pytest
  from numpy import pi
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from ..None import eulerangles
  from ..None import quaternions
label_desc: Use image node_id 3 for calling a global function with example usage: z_only(z) and returns: np