code: def _reference_pde_initial_cond(xs):
      """Initial conditions for the reference diffusion equation."""
      return -tf.math.abs(xs - 0.5) + 0.5
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  import tf_quant_finance
  from tensorflow.python.framework import test_util
label_desc: Use image node_id 6 for calling a global function with example usage: _reference_pde_initial_cond(xs) and returns: unknown