class_docstr: Loader for sliding history windows, with support for adjustments.
  
  Parameters
  ----------
  trading_calendar: TradingCalendar
      Contains the grouping logic needed to assign minutes to periods.
  reader : DailyBarReader, MinuteBarReader
      Reader for pricing bars.
  adjustment_reader : SQLiteAdjustmentReader
      Reader for adjustment data.
class_docstr_tok: ["Loader","for","sliding","history","windows",",","with","support","for","adjustments",".","Parameters","--","--","--","--","--","trading_calendar",":","TradingCalendar","Contains","the","grouping","logic","needed","to","assign","minutes","to","periods",".","reader",":","DailyBarReader",",","MinuteBarReader","Reader","for","pricing","bars",".","adjustment_reader",":","SQLiteAdjustmentReader","Reader","for","adjustment","data","."]
code: def __init__(
      self,
      trading_calendar,
      reader,
      equity_adjustment_reader,
      asset_finder,
      roll_finders=None,
      sid_cache_size=1000,
      prefetch_length=0,
  ):
      self.trading_calendar = trading_calendar
      self._asset_finder = asset_finder
      self._reader = reader
      self._adjustment_readers = {}
      if equity_adjustment_reader is not None:
          self._adjustment_readers[
              Equity
          ] = HistoryCompatibleUSEquityAdjustmentReader(
              equity_adjustment_reader
          )
      if roll_finders:
          self._adjustment_readers[
              ContinuousFuture
          ] = ContinuousFutureAdjustmentReader(
              trading_calendar,
              asset_finder,
              reader,
              roll_finders,
              self._frequency,
          )
      self._window_blocks = {
          field: ExpiringCache(LRU(sid_cache_size))
          for field in self.FIELDS
      }
      self._prefetch_length = prefetch_length
  
imports: from abc import ABCMeta, abstractmethod, abstractproperty
  from numpy import concatenate
  from lru import LRU
  from pandas import isnull
  from pandas.tslib import normalize_date
  from toolz import sliding_window
  from six import with_metaclass
  from catalyst.assets import Equity, Future
  from catalyst.assets.continuous_futures import ContinuousFuture
  from catalyst.lib._int64window import AdjustedArrayWindow
  from catalyst.lib._float64window import AdjustedArrayWindow
  from catalyst.lib.adjustment import Float64Multiply, Float64Add
  from catalyst.utils.cache import ExpiringCache
  from catalyst.utils.math_utils import number_of_decimal_places
  from catalyst.utils.memoize import lazyval
  from catalyst.utils.numpy_utils import float64_dtype
  from catalyst.utils.pandas_utils import find_in_sorted_index
label_desc: Use image node_id 1 to create a new HistoryLoader object from inherited base classes:  with example: obj = HistoryLoader(trading_calendar, reader, equity_adjustment_reader, asset_finder, roll_finders, sid_cache_size, prefetch_length)