class_docstr: Helper class to allow construction of a list without
  having to reverse it in the end.
code: def append_elem(self, elem):
      return self._append(elem, lambda e: PList(e, _EMPTY_PLIST))
  
imports: from ._compat import Sequence, Hashable
  from numbers import Integral
  from functools import reduce
label_desc: Use image node_id 3 for calling the _PListBuilder obj's underlying member method code with example usage: obj.append_elem(elem) and returns: self