code: def check_abbreviation_unique(self, abbreviation, newFilterPattern, targetItem):
          
          for item in self.allFolders:
              if model.TriggerMode.ABBREVIATION in item.modes:
                  if abbreviation in item.abbreviations and item.filter_matches(newFilterPattern):
                      return item is targetItem, item
              
          for item in self.allItems:
              if model.TriggerMode.ABBREVIATION in item.modes:
                  if abbreviation in item.abbreviations and item.filter_matches(newFilterPattern):
                      return item is targetItem, item
  
          return True, None
docs: Checks that the given abbreviation is not already in use.
          
          @param abbreviation: the abbreviation to check
          @param newFilterPattern:
          @param targetItem: the phrase for which the abbreviation to be used