input: from typing import List
  
  def evaluate_expression(expr: str) -> float:
      """Given a string containing a valid numerical expression, evaluate the expression and return the result as a float.
      
      >>> evaluate_expression('10 + 20')
      30.0
      >>> evaluate_expression('5 * 6')
      30.0
      >>> evaluate_expression('100 / 2')
      50.0
      """
output:     return eval(expr)