class_docstr: Base class which does the calculation of the AroonUp/AroonDown values and
  defines the common parameters.
  
  It uses the class attributes _up and _down (boolean flags) to decide which
  value has to be calculated.
  
  Values are not assigned to lines but rather stored in the "up" and "down"
  instance variables, which can be used by subclasses to for assignment or
  further calculations
code: def __init__(self):
      # Look backwards period + 1 for current data because the formula mus
      # produce values between 0 and 100 and can only do that if the
      # calculated hhidx/llidx go from 0 to period (hence period + 1 values)
      idxperiod = self.p.period + 1
  
      if self._up:
          hhidx = FindFirstIndexHighest(
              self.data.high, period=idxperiod
          )
          self.up = (100.0 / self.p.period) * (self.p.period - hhidx)
  
      if self._down:
          llidx = FindFirstIndexLowest(self.data.low, period=idxperiod)
          self.down = (100.0 / self.p.period) * (self.p.period - llidx)
  
      super(_AroonBase, self).__init__()
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  from .None import Indicator, FindFirstIndexHighest, FindFirstIndexLowest
label_desc: Use image node_id 3 to create a new _AroonBase object from inherited base classes: Indicator with example: obj = _AroonBase()