'Update the index entry if any of the given fields are in SEARCH_TARGET_DICT. (doesn\'t save
the changes, just changes them in the entry dict)
:param index_entry:
:param fields: a dictionary of fields and values usually only those explicitly set and already
ready for persisting (e.g., references converted to block_ids)'

def _update_search_targets(self, index_entry, fields):

    for (field_name, field_value) in fields.iteritems():
        if (field_name in self.SEARCH_TARGET_DICT):
            index_entry.setdefault('search_targets', {})[field_name] = field_value
