class_docstr: Determine the relative weighting and leverage of the pairs trade
  
  Args:
      * weight( float ): The weight to put on the buy trade
  Sets:
      * weights
code: def __init__(self, weight):
      self.weight = weight
  
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 1 to create a new WeighPair object from inherited base classes: bt with example: obj = WeighPair(weight)