def METHOD_NAME(self):
    """TreesMap().load() populates trees map"""
    trees_map = TreesMap([THREAD_TYPE])
    self.assertFalse(
        trees_map.is_loaded, "trees map should be not loaded by default"
    )
    trees_map.load()
    self.assertTrue(
        trees_map.is_loaded, "trees map should be loaded after call to load()"
    )
    self.assertEqual(len(trees_map.types), 1, "expected to load one type")
    self.assertEqual(len(trees_map.trees), 1, "expected to load one tree")
    self.assertEqual(len(trees_map.roots), 1, "expected to load one root")
    tree_id = Category.objects.get(special_role="root_category").tree_id
    self.assertIn(
        "root_category", trees_map.types, "invalid thread type was loaded"
    )
    self.assertEqual(
        trees_map.trees[tree_id].root_name,
        "root_category",
        "invalid tree was loaded",
    )
    self.assertIn("root_category", trees_map.roots, "invalid root was loaded")