input: 
  
  def change_base(x: int, base: int):
      """Change numerical base of input number x to base.
      return string representation after the conversion.
      base numbers are less than 10.
      >>> change_base(8, 3)
      '22'
      >>> change_base(8, 2)
      '1000'
      >>> change_base(7, 2)
      '111'
      """
  
output:     result = ""
      while x > 0:
          result = str(x % base) + result
          x //= base
      return result