docs: def load (self, filename):
          """Loads Command Definitions from the given YAML file into this
          Command Dictionary.
          """
          if self.filename is None:
              self.filename = filename
  
          stream = open(self.filename, "rb")
          for doc in yaml.load_all(stream):
              for table in doc:
                  self.add(table)
          stream.close()