code: def get_node_sum(self, age=None):
          
          if age is None:
              age = self.age
  
          return age if self.comp == 1 else int((pow(self.comp, age+1) - 1) / (self.comp - 1))
docs: Get sum of all branches in the tree.
  
          Returns:
              int: The sum of all nodes grown until the age.