class_docstr: Magic part of the protocol for multiple value returns.
  
  See `ProgramBuilder.__call__`.
code: def pattern(self, item):
      # _MagicPattern is meant to be a friend class of ProgramBuilder.
      # pylint: disable=protected-access
      if item is not None:
          self._context._update_last_instruction(
              item.replace(
                  vars_out=inst.pattern_map(str, self._pattern)
              )
          )
      for var in inst.pattern_traverse(self._pattern):
          self._context._mark_defined(var)
  
imports: import collections
  import contextlib
  import inspect
  from tensorflow_probability.python.experimental.auto_batching import instructions
label_desc: Use image node_id 3 for calling the _MagicPattern obj's underlying member method code with example usage: obj.pattern(item) without return types