class_docstr: A ``RecursiveDescentParser`` that allows you to step through the
  parsing process, performing a single operation at a time.
  
  The ``initialize`` method is used to start parsing a text.
  ``expand`` expands the first element on the frontier using a single
  CFG production, and ``match`` matches the first element on the
  frontier against the next text token. ``backtrack`` undoes the most
  recent expand or match operation.  ``step`` performs a single
  expand, match, or backtrack operation.  ``parses`` returns the set
  of parses that have been found by the parser.
  
  :ivar _history: A list of ``(rtext, tree, frontier)`` tripples,
      containing the previous states of the parser.  This history is
      used to implement the ``backtrack`` operation.
  :ivar _tried_e: A record of all productions that have been tried
      for a given tree.  This record is used by ``expand`` to perform
      the next untried production.
  :ivar _tried_m: A record of what tokens have been matched for a
      given tree.  This record is used by ``step`` to decide whether
      or not to match a token.
  :see: ``nltk.grammar``
docstr: :return: Whether the parser's current state represents a
      complete parse.
  :rtype: bool
docstr_tok: [":","return",":","Whether","the","parser","'s","current","state","represents","a","complete","parse",".",":","rtype",":","bool"]
code: def currently_complete(self):
      """
      :return: Whether the parser's current state represents a
          complete parse.
      :rtype: bool
      """
      return len(self._frontier) == 0 and len(self._rtext) == 0
  
imports: from nltk.grammar import Nonterminal
  from nltk.parse.api import ParserI
  from nltk.tree import ImmutableTree, Tree
label_desc: Use image node_id 15 for calling the SteppingRecursiveDescentParser obj's underlying member method code with example usage: obj.currently_complete() and returns: unknown