code: def binary_search_file(file, key, cache=None, cacheDepth=-1):
      """
      Return the line from the file with first word key.
      Searches through a sorted file using the binary search algorithm.
  
      :type file: file
      :param file: the file to be searched through.
      :type key: str
      :param key: the identifier we are searching for.
      """
  
      key = key + " "
      keylen = len(key)
      start = 0
      currentDepth = 0
  
      if hasattr(file, "name"):
          end = os.stat(file.name).st_size - 1
      else:
          file.seek(0, 2)
          end = file.tell() - 1
          file.seek(0)
  
      if cache is None:
          cache = {}
  
      while start < end:
          lastState = start, end
          middle = (start + end) // 2
  
          if cache.get(middle):
              offset, line = cache[middle]
  
          else:
              line = ""
              while True:
                  file.seek(max(0, middle - 1))
                  if middle > 0:
                      file.discard_line()
                  offset = file.tell()
                  line = file.readline()
                  if line != "":
                      break
                  # at EOF; try to find start of the last line
                  middle = (start + middle) // 2
                  if middle == end - 1:
                      return None
              if currentDepth < cacheDepth:
                  cache[middle] = (offset, line)
  
          if offset > end:
              assert end != middle - 1, "infinite loop"
              end = middle - 1
          elif line[:keylen] == key:
              return line
          elif line > key:
              assert end != middle - 1, "infinite loop"
              end = middle - 1
          elif line < key:
              start = offset + len(line) - 1
  
          currentDepth += 1
          thisState = start, end
  
          if lastState == thisState:
              # Detects the condition where we're searching past the end
              # of the file, which is otherwise difficult to detect
              return None
  
      return None
  
imports: import inspect
  import locale
  import os
  import pydoc
  import re
  import textwrap
  import unicodedata
  import warnings
  from collections import defaultdict, deque
  from itertools import chain, combinations, islice, tee
  from pprint import pprint
  from urllib.request import HTTPPasswordMgrWithDefaultRealm, ProxyBasicAuthHandler, ProxyDigestAuthHandler, ProxyHandler, build_opener, getproxies, install_opener
  from nltk.collections import *
  from nltk.internals import deprecated, raise_unorderable_types, slice_bounds
label_desc: Use image node_id 33 for calling a global function with example usage: binary_search_file(file, key, cache, cacheDepth) and returns: None, None, line, None