code: def implicit(vals):
      x = vals[:, 0]
      y = vals[:, 1]
      z = vals[:, 2]
      return x**2 - y**2 * z**2 + z**3
  
file_path: nipy/nipy/core/reference/tests/test_parametrized_surface.py
imports: import numpy
  from nipy.core.api import CoordinateMap, CoordinateSystem, Grid
label_desc: Use image node_id 2 for calling a global function with example usage: implicit(vals) and returns: unknown