code: def create(cls, name, user_group=None, activation_date=None,
          expiration_date=None, comment=None):
          
          json = {
              'name': name,
              'unique_id': 'cn={},{}'.format(name, InternalUserDomain.user_dn),
              'comment': comment}
          
          limits = {'activation_date': activation_date, 'expiration_date': expiration_date}
          for attr, value in limits.items():
              json[attr] = datetime_to_ms(value) if value else None
              
          if user_group:
              json.update(user_group=element_resolver(user_group))
  
          return ElementCreator(cls, json)
docs: Create an internal user. 
          Add a user example::
          
              InternalUser.create(name='goog', comment='my comment')
              
          :param str name: name of user that is displayed in SMC    
          :param list(str,InternalUserGroup) user_group: internal user groups
              which to add this user to.
          :param datetime activation_date: activation date as datetime object.
              Activation date only supports year and month/day
          :param datetime expiration_date: expiration date as datetime object.
              Expiration date only supports year and month/day
          :param str comment: optional comment
          :raises ElementNotFound: thrown if group specified does not exist
          :rtype: InternalUser