Use
Code:
set_field(self, name, book_id_to_val_map, allow_case_change=True, do_path_update=True)
'''
Set the values of the field specified by ``name``. Returns the set of all book ids that were affected by the change.
:param book_id_to_val_map: Mapping of book_ids to values that should be applied.
:param allow_case_change: If True, the case of many-one or many-many fields will be changed.
For example, if a book has the tag ``tag1`` and you set the tag for another book to ``Tag1``
then the both books will have the tag ``Tag1`` if allow_case_change is True, otherwise they will
both have the tag ``tag1``.
:param do_path_update: Used internally, you should never change it.
'''
in cache.py (new_api)