class_docstr: Affine transformation class
  
  Parameters
  ----------
  matrix : array-like | None
      4x4 array to use for the transform.
code: def matrix(self):
      return self._matrix
  
imports: from __future__ import division
  import numpy
  from ...util import transforms
  from ...geometry import Rect
  from ._util import arg_to_vec4, as_vec4
  from .base_transform import BaseTransform
label_desc: Use image node_id 6 for calling the MatrixTransform obj's underlying member method code with example usage: obj.matrix() and returns: self