code: def _exec(self, binary, stdin='', args=(), env={}):
          
  
          call_kw = self._gen_call_kws(**env)
          call_args = [self._get_exec_binary(call_kw)]
          call_args.extend(args)
          return fork_exec(call_args, stdin, **call_kw)
docs: Executes the binary using stdin and args with environment
          variables.
  
          Returns a tuple of stdout, stderr.  Format determined by the
          input text (either str or bytes), and the encoding of str will
          be determined by the locale this module was imported in.