def add_nodes(self, nodelist):
for each in nodelist:<EOL><INDENT>self.add_node(each)<EOL><DEDENT>
Add given nodes to the graph.

@attention: While nodes can be of any type, it's strongly recommended to use only
numbers and single-line strings as node identifiers if you intend to use write().
Objects used to identify nodes absolutely must be hashable. If you need attach a mutable
or non-hashable node, consider using the labeling feature.

@type  nodelist: list
@param nodelist: List of nodes to be added to the graph.