code: def installHandler():
      global _interrupt_handler
      if _interrupt_handler is None:
          default_handler = signal.getsignal(signal.SIGINT)
          _interrupt_handler = _InterruptHandler(default_handler)
          signal.signal(signal.SIGINT, _interrupt_handler)
  
file_path: cpython/Lib/unittest/signals.py
imports: import signal
  import weakref
  from functools import wraps
label_desc: Use image node_id 3 for calling a global function with example usage: installHandler() without return types