input:                     
  from typing import List
  
  
  def avg_list(lst: List[float]) -> float:
      """ Calculate the average of a list of numbers.
      >>> avg_list([1.0, 2.0, 3.0, 4.0])
      2.5
      >>> avg_list([5.0, 10.0, 15.0])
      10.0
      """
output:     if not lst:
          return 0.0
      return sum(lst) / len(lst)