class_docstr: Realtime clock for live trading.
  
  This class is a drop-in replacement for
  :class:`zipline.gens.sim_engine.MinuteSimulationClock`.
  
  This is a stripped down version because crypto exchanges run
  around the clock.
  
  The :param:`time_skew` parameter represents the time difference between
  the Broker and the live trading machine's clock.
code: def __init__(
      self, sessions, time_skew=pd.Timedelta("0s"), start=None, end=None
  ):
      self.sessions = sessions
      self.time_skew = time_skew
      self._last_emit = None
      self._before_trading_start_bar_yielded = True
      self.start = start
      self.end = end
  
file_path: catalyst/catalyst/exchange/simple_clock.py
imports: from time import sleep
  import pandas
  from catalyst.constants import LOG_LEVEL
  from catalyst.gens.sim_engine import BAR, SESSION_START, SESSION_END
  from logbook import Logger
label_desc: Use image node_id 1 to create a new SimpleClock object from inherited base classes: object with example: obj = SimpleClock(sessions, time_skew, start, end)