input: Write a function to generate a Python program that prints out every number from 0 to 10, but with every number being multiplied by 2. The function should return the string representation of the Python program. If the input is invalid, the function should return "Invalid input".
  
  assert generate_program()=="""for i in range(11):\n print(i*2)"""
  assert generate_program(invalid_input)="Invalid input"
output: def generate_program(input=None):
      if input is not None:
          return "Invalid input"
      return "for i in range(11):\n print(i*2)"