class_docstr: Dynamically create a new sub-strategy (with common logic) for every pairs trade.
  
  Args:
      * trade_algos ([Algo]): List of algos that defines the sub-strategy behavior
code: def __call__(self, target):
      pairs = target.temp.get("pairs", None)
      if pairs is None or pairs.empty:
          return True
  
      target.temp["weights"] = {}
      for (sell, buy), signal in iteritems(target.temp["pairs"]):
          trade_name = "%s_%s" % (buy, sell)
          if trade_name not in target.children:
              trade = bt.Strategy(
                  trade_name,
                  deepcopy(self.trade_algos),
                  children=[buy, sell],
                  parent=target,
              )
              trade.setup_from_parent(buy=buy, sell=sell)
              target.temp["weights"][trade_name] = 0
  
      return True
  
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 SetupPairsTrades obj's underlying member method code with example usage: obj.__call__(target) and returns: True, True