class_docstr: Affine warp constraints class.
  
  `AffineWarpConstraints` allow for
  very succinct definitions of constraints on
  the values of entries in affine transform matrices.
docstr: Combines two constraints,
  raising an error if they are not compatible.
docstr_tok: ["Combines","two","constraints",",","raising","an","error","if","they","are","not","compatible","."]
code: def _combine(self, x, y):
      """
      Combines two constraints,
      raising an error if they are not compatible.
      """
      if x is None or y is None:
          return x or y
      if x != y:
          tf.logging.fatal("Incompatible set of constraints provided.")
          raise ValueError
      return x
  
imports: from __future__ import absolute_import, division, print_function
  from itertools import chain
  import numpy
  import tensorflow
  from niftynet.layer.base_layer import Layer, LayerFromCallable, Invertible
label_desc: Use image node_id 7 for calling the AffineWarpConstraints obj's underlying member method code with example usage: obj._combine(x, y) and returns: x, unknown