input: from typing import List
  
  def get_max_value(numbers: List[float]) -> float:
      """
      Returns the largest value from a given list of numbers.
      
      >>> get_max_value([2, 4, 1, 6])
      6
      >>> get_max_value([-10, -5, -1, -20])
      -1
      >>> get_max_value([10.5, 20.2, 15.8, 25.1])
      25.1
      """
output:     if not numbers:
          return float('-inf')
      max_value = numbers[0]
      for num in numbers:
          if num > max_value:
              max_value = num
      return max_value