code: def get_child_edge(cls, index, left_parent, right_parent):
          
          [ed1, ed2, depend_set] = cls._identify_eds_ing(left_parent, right_parent)
          left_u, right_u = cls.get_conditional_uni(left_parent, right_parent)
          X = np.array([[x, y] for x, y in zip(left_u, right_u)])
          name, theta = Bivariate.select_copula(X)
          new_edge = Edge(index, ed1, ed2, name, theta)
          new_edge.D = depend_set
          new_edge.parents = [left_parent, right_parent]
          return new_edge
docs: Construct a child edge from two parent edges.