class_docstr: A base class providing the backwards-compatible spawn API for Pexpect.
  
  This should not be instantiated directly: use :class:`pexpect.spawn` or
  :class:`pexpect.fdpexpect.fdspawn`.
docstr: This is the common loop used inside expect. The 'searcher' should be
  an instance of searcher_re or searcher_string, which describes how and
  what to search for in the input.
  
  See expect() for other arguments, return value and exceptions. 
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code: def expect_loop(self, searcher, timeout=-1, searchwindowsize=-1):
      """This is the common loop used inside expect. The 'searcher' should be
      an instance of searcher_re or searcher_string, which describes how and
      what to search for in the input.
  
      See expect() for other arguments, return value and exceptions."""
  
      exp = Expecter(self, searcher, searchwindowsize)
      return exp.expect_loop(timeout)
  
imports: from io import StringIO, BytesIO
  import codecs
  import os
  import sys
  import re
  import errno
  from .exceptions import ExceptionPexpect, EOF, TIMEOUT
  from .expect import Expecter, searcher_string, searcher_re
label_desc: Use image node_id 14 for calling the SpawnBase obj's underlying member method code with example usage: obj.expect_loop(searcher, timeout, searchwindowsize) and returns: exp