code: def expect_document_root(self):
      self.states.append(self.expect_document_end)
      self.expect_node(root=True)
  
imports: from .error import YAMLError
  from .events import *
label_desc: Use image node_id 12 for calling the Emitter obj's underlying member method code with example usage: obj.expect_document_root() without return types