def query(self, query):
    '''Returns an iterable of objects matching criteria expressed in `query`
    FSDatastore.query queries all the `.obj` files within the directory
    specified by the query.key.

    Args:
      query: Query object describing the objects to return.

    Raturns:
      Cursor with all objects matching criteria
    '''
    path = self.path(query.key)

    if os.path.exists(path):
      filenames = os.listdir(path)
      filenames = list(set(self.ignore_list) - set(filenames))
      filenames = map(lambda f: os.path.join(path, f), filenames)
      iterable = self._read_object_gen(filenames)
    else:
      iterable = list()

    return query(iterable) # must apply filters, etc naively.
dataset/ETHPy150Open datastore/datastore/datastore/filesystem/__init__.py/FileSystemDatastore.query/swapped operands of `-`