code: def _matrix_constrainer(support):
      """Helper for `constrainer` for matrix supports."""
      constrainers = {
          Support.MATRIX_UNCONSTRAINED: identity_fn,
          Support.MATRIX_POSITIVE_DEFINITE: positive_definite,
          Support.MATRIX_LOWER_TRIL_POSITIVE_DEFINITE: lower_tril_positive_definite,
          Support.MATRIX_LOWER_TRIL: lower_tril,
      }
      if support not in constrainers:
          raise NotImplementedError(support)
      return constrainers[support]
  
imports: import contextlib
  import os
  import re
  import traceback
  import unittest
  import hypothesis
  from hypothesis.extra import numpy
  import hypothesis.strategies
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import dtype_util
  from tensorflow_probability.python.internal import tensorshape_util
  from tensorflow_probability.python.util.deferred_tensor import DeferredTensor
label_desc: Use image node_id 15 for calling a global function with example usage: _matrix_constrainer(support) and returns: constrainers