code: def suite():
      vertex_coloring_suite = (
          unittest.defaultTestLoader.loadTestsFromTestCase(
              VertexColoringTests
          )
      )
      return unittest.TestSuite([vertex_coloring_suite])
  
imports: import unittest
  from igraph import Graph
label_desc: Use image node_id 2 for calling a global function with example usage: suite() and returns: unittest