class_docstr: A file-ish object that can have new data loaded into it.
  
  You can also push and pop line-matching predicates onto a stack.  When the
  current predicate matches the current line, a false EOF response
  (i.e. empty string) is returned instead.  This lets the parser adhere to a
  simple abstraction -- it parses until EOF closes the current message.
class_docstr_tok: ["A","file-ish","object","that","can","have","new","data","loaded","into","it",".","You","can","also","push","and","pop","line-matching","predicates","onto","a","stack",".","When","the","current","predicate","matches","the","current","line",",","a","false","EOF","response","(","i.e",".","empty","string",")","is","returned","instead",".","This","lets","the","parser","adhere","to","a","simple","abstraction","--","it","parses","until","EOF","closes","the","current","message","."]
code: def unreadline(self, line):
      # Let the consumer push a line back into the buffer.
      assert line is not NeedMoreData
      self._lines.appendleft(line)
  
imports: import re
  from email import errors
  from email._policybase import compat32
  from collections import deque
  from io import StringIO
label_desc: Use image node_id 6 for calling the BufferedSubFile obj's underlying member method code with example usage: obj.unreadline(line) without return types