code: def add_locus(self,inlocus):
      
      if self.use_direction == True and inlocus.use_direction == False:
        sys.stderr.write("ERROR if using the direction in Loci, then every locus added needs use_direction to be True\n")
        sys.exit()
      self.loci.append(inlocus)
      return
docs: Adds a locus to our loci, but does not go through an update our locus sets yet