code: def __add__(self, other):
      if self.dim != other.dim:
          return None
      con = contrast(self.dim)
      con.type = self.type
      con.effect = self.effect + other.effect
      con.variance = self.variance + other.variance
      con.dof = self.dof + other.dof
      return con
  
imports: import numpy
  import scipy.stats
  from nipy.algorithms.statistics.utils import z_score
  from ..utils import mahalanobis
  from .None import kalman
label_desc: Use image node_id 6 for calling the contrast obj's underlying member method code with example usage: obj.__add__(other) and returns: con, None