code: def addChild(self, childJob):
          
          self._children.append(childJob)
          childJob._addPredecessor(self)
          return childJob
docs: Adds childJob to be run as child of this job. Child jobs will be run \
          directly after this job's :func:`toil.job.Job.run` method has completed.
  
          :param toil.job.Job childJob:
          :return: childJob
          :rtype: toil.job.Job