old_contents: from django import forms
  
  
  class FilemanagerFormField(forms.CharField):
      pass
  
new_contents: from django import forms
  from django.forms.widgets import Input
  
  
  class FilemanagerWidget(Input):
      pass
  
  
  class FilemanagerFormField(forms.CharField):
      pass
  
subject: create empty widget class for filemanager