class_docstr: dz is imposed by user; accounts for scaling if any.
class_docstr_tok: ["dz","is","imposed","by","user",";","accounts","for","scaling","if","any","."]
code: def compute_dz(self, dz):
      (dzdx, dzdy) = dz
      dzdx = dzdx * self._unit_x
      dzdy = dzdy * self._unit_y
      return np.vstack([dzdx, dzdy]).T
  
imports: import numpy
  from matplotlib import _api
  from matplotlib.tri import Triangulation
  from matplotlib.tri._trifinder import TriFinder
  from matplotlib.tri._tritools import TriAnalyzer
label_desc: Use image node_id 1 for calling the _DOF_estimator_user obj's underlying member method code with example usage: obj.compute_dz(dz) and returns: np