code: def _frequency(self):
      return "daily"
  
imports: from abc import ABCMeta, abstractmethod, abstractproperty
  from numpy import concatenate
  from lru import LRU
  from pandas import isnull
  from toolz import sliding_window
  from six import with_metaclass
  from zipline.assets import Equity, Future
  from zipline.assets.continuous_futures import ContinuousFuture
  from zipline.lib._int64window import AdjustedArrayWindow
  from zipline.lib._float64window import AdjustedArrayWindow
  from zipline.lib.adjustment import Float64Multiply, Float64Add
  from zipline.utils.cache import ExpiringCache
  from zipline.utils.math_utils import number_of_decimal_places
  from zipline.utils.memoize import lazyval
  from zipline.utils.numpy_utils import float64_dtype
  from zipline.utils.pandas_utils import find_in_sorted_index, normalize_date
label_desc: Use image node_id 1 for calling the DailyHistoryLoader obj's underlying member method code with example usage: obj._frequency() and returns: str