class_docstr: It is a variation of the AroonUpDown indicator which shows the current
  difference between the AroonUp and AroonDown value, trying to present a
  visualization which indicates which is stronger (greater than 0 -> AroonUp
  and less than 0 -> AroonDown)
  
  Formula:
    - aroonosc = aroonup - aroondown
  
  See:
    - http://stockcharts.com/school/doku.php?id=chart_school:technical_indicators:aroon
code: def __init__(self):
      super(AroonOscillator, self).__init__()
  
      self.lines.aroonosc = self.up - self.down
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  from .None import Indicator, FindFirstIndexHighest, FindFirstIndexLowest
label_desc: Use image node_id 2 to create a new AroonOscillator object from inherited base classes: _AroonBase with example: obj = AroonOscillator()