def add_item(self, item_subtype, item):
"""add a personal copy of a item to a user's account
Arguments:
item - Item object being attached to the User
Return Value:
a ItemCopy instance that links the User to the Item; None if the Item could not be linked
"""
from src.items.models import ItemCopy
itemcopy = ItemCopy(item=item.key, owner=self.key, item_subtype=item_subtype)
if itemcopy.put():
self.item_count = self.item_count + 1
self.put()
return itemcopy
