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: Expose file descriptor for a file-like interface
          
docstr_tok: ["Expose","file","descriptor","for","a","file-like","interface"]
code: def fileno(self):
      """Expose file descriptor for a file-like interface"""
      return self.child_fd
  
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 19 for calling the SpawnBase obj's underlying member method code with example usage: obj.fileno() and returns: self