input: Write a python function to draw a diamond shape using stars.
  assert draw_diamond(3) == """
    * 
   * * 
  * * * 
   * * 
    * 
  """
  assert draw_diamond(4) == """
     * 
    * * 
   * * * 
  * * * * 
   * * * 
    * * 
     * 
  """
  assert draw_diamond(2) == """
   * 
  * * 
   * 
  """
output: def draw_diamond(n):
      diamond = []
      for i in range(n):
          diamond.append(" " * (n - i - 1) + "* " * (i + 1))
      for i in range(n - 1):
          diamond.append(" " * (i + 1) + "* " * (n - i - 1))
      return "\n".join(line.rstrip() for line in diamond) + "\n"