old_contents: import sys
  
  from .proxy import Proxy
  
  def load(info):
      info['apiRoot'].proxy = Proxy()
  
new_contents: import sys
  from girder.models.model_base import ValidationException
  from girder import events
  from .proxy import Proxy
  
  import constants
  
  def validate_settings(event):
      key = event.info['key']
  
      if key == constants.PluginSettings.PROXY_FILE_PATH:
          event.preventDefault().stopPropagation()
  
  
  
  def load(info):
      events.bind('model.setting.validate', 'pvwproxy', validate_settings)
      info['apiRoot'].proxy = Proxy()
  
subject: Add settng validation function