code: def test_get_parent_root(self):
      root_node = self.tree.get_node_from_id("T051")
      parent = self.tree.get_parent(root_node)
      assert parent is None
  
file_path: scispacy/tests/test_umls_semantic_type_tree.py
imports: import unittest
  from scispacy.umls_semantic_type_tree import construct_umls_tree_from_tsv
label_desc: Use image node_id 4 for calling the TestUmlsSemanticTypeTree obj's underlying member method code with example usage: obj.test_get_parent_root() without return types