dgr_graph, query a node in
the graph (using the node ID) and perform operations on the type definition
for that node.
node_type(graph, node, action = "read", value = NULL)dgr_graph that is created
using create_graph.delete,
remove, or drop. To add a type definition to a node with no
type set, use add or create. To update a node's type
definition, use update. To return the value of a node type, use
read. To determine whether there is a type set for the selected node,
use check.dgr_graph.