input: from typing import Callable
  
  def generate_fibonacci_function() -> Callable[[int], int]:
      """ Generate a Python function to calculate the Fibonacci number at a given position.
      >>> fib = generate_fibonacci_function()
      >>> fib(10)
      55
      >>> fib(0)
      0
      """
      def fibonacci(n: int) -> int:
          if n == 0:
              return 0
          elif n == 1:
              return 1
          else:
              return fibonacci(n-1) + fibonacci(n-2)
      return fibonacci
output:     def fibonacci(n: int) -> int:
          if n == 0:
              return 0
          elif n == 1:
              return 1
          else:
              a, b = 0, 1
              for _ in range(2, n + 1):
                  a, b = b, a + b
              return b
      return fibonacci