code: def _pressModifiers(self, modifiers, pressed=True, globally=False):
          
          if not isinstance(modifiers, list):
              raise TypeError('Please provide modifiers in list form')
  
          if not hasattr(self, 'keyboard'):
              self.keyboard = AXKeyboard.loadKeyboard()
  
          modFlags = 0
  
          # Press given modifiers
          for nextMod in modifiers:
              if nextMod not in self.keyboard:
                  errStr = 'Key %s not found in keyboard layout'
                  self._clearEventQueue()
                  raise ValueError(errStr % self.keyboard[nextMod])
              modEvent = Quartz.CGEventCreateKeyboardEvent(
                  Quartz.CGEventSourceCreate(0),
                  self.keyboard[nextMod],
                  pressed
              )
              if not pressed:
                  # Clear the modflags:
                  Quartz.CGEventSetFlags(modEvent, 0)
              if globally:
                  self._queueEvent(Quartz.CGEventPost, (0, modEvent))
              else:
                  # To direct output to the correct application need the PSN (macOS <=10.10) or PID(macOS > 10.10):
                  macVer, _, _ = platform.mac_ver()
                  macVer = int(macVer.split('.')[1])
                  if macVer > 10:
                      appPid = self._getPid()
                      self._queueEvent(Quartz.CGEventPostToPid, (appPid, modEvent))
                  else:
                      appPsn = self._getPsnForPid(self._getPid())
                      self._queueEvent(Quartz.CGEventPostToPSN, (appPsn, modEvent))
              # Add the modifier flags
              modFlags += AXKeyboard.modKeyFlagConstants[nextMod]
  
          return modFlags
docs: Press given modifiers (provided in list form).
  
          Parameters: modifiers list, global or app specific
          Optional: keypressed state (default is True (down))
          Returns: Unsigned int representing flags to set