input: from typing import List
  
  def predict_customer_ltv(customer_transactions: List[List[float]]) -> float:
      """ Predicts the customer lifetime value (LTV) given a list of past transactions for the customer.
      Each transaction is represented as a list of features.
      >>> predict_customer_ltv([[10.0, 100.0, 5.0], [15.0, 120.0, 7.0], [20.0, 150.0, 10.0]])
      1200.5
      >>> predict_customer_ltv([[5.0, 50.0, 3.0], [7.0, 70.0, 4.0], [9.0, 90.0, 6.0]])
      750.0
      """
output:     total_value = 0.0
      for transaction in customer_transactions:
          total_value += transaction[0] * transaction[1] * transaction[2]
      return total_value / len(customer_transactions)