code: def add_edge_attributes(self, edge, attrs):
          
          for attr in attrs:
              self.add_edge_attribute(edge, attr)
docs: Append a sequence of attributes to the given edge
          
          @type  edge: edge
          @param edge: One edge.
  
          @type  attrs: tuple
          @param attrs: Node attributes specified as a sequence of tuples in the form (attribute, value).