code: def test_add_node_nonstring(self):
      self.graph = DAG()
      self.graph.add_node(1)
  
      self.graph = DAG()
      self.graph.add_node(1, latent=True)
  
imports: import unittest
  import networkx
  import numpy
  import pgmpy.tests.help_functions
  from pgmpy.base import DAG, PDAG
label_desc: Use image node_id 5 for calling the TestDAGCreation obj's underlying member method code with example usage: obj.test_add_node_nonstring() without return types