code: def _mock_apply_fn(self, target, source):
      target = parser.unparse(target, include_encoding_marker=False)
      source = parser.unparse(source, include_encoding_marker=False)
      self._invocation_counts[(target.strip(), source.strip())] += 1
  
imports: import ast
  import collections
  import textwrap
  import gast
  from tensorflow.python.autograph.pyct import anno
  from tensorflow.python.autograph.pyct import ast_util
  from tensorflow.python.autograph.pyct import loader
  from tensorflow.python.autograph.pyct import parser
  from tensorflow.python.autograph.pyct import pretty_printer
  from tensorflow.python.autograph.pyct import qual_names
  from tensorflow.python.platform import test
label_desc: Use image node_id 16 for calling the AstUtilTest obj's underlying member method code with example usage: obj._mock_apply_fn(target, source) without return types