docs: def start(self):
          """
          Start executor with additional checks.
  
          Checks if previous executor isn't running then start process
          (executor) and wait until it's started.
          :returns: itself
          :rtype: Executor
          """
          if self.pre_start_check():
              # Some other executor (or process) is running with same config:
              raise AlreadyRunning(self)
  
          super(Executor, self).start()
  
          self.wait_for(self.check_subprocess)
          return self