class_docstr: Control flow algo that only returns True if the price of the target crosses the threshold
  
  Args
      * threshold (float): The price threshold
      * is_greater (bool): Whether to do return True when price exceeds the threshold
code: def __call__(self, target):
      if self.is_greater:
          return target.price >= self.threshold
      else:
          return target.price < self.threshold
  
imports: from copy import deepcopy
  from future.utils import iteritems
  from datetime import date
  import pandas
  import numpy
  import bt
label_desc: Use image node_id 2 for calling the PriceCompare obj's underlying member method code with example usage: obj.__call__(target) and returns: unknown, unknown