input: Write a function to modify the given Python code so that it raises a `TypeError` exception if the input value is not an integer.
  
  ### Input:
  def square_root(x):
      return x**0.5
  
  ### Output:
  def square_root(x):
      if not isinstance(x, int):
          raise TypeError('Input must be an integer')
      return x**0.5
  
  assert square_root(4) == 2
  assert square_root(9) == 3
  try:
      square_root('a')
      assert False
  except TypeError:
      assert True
  try:
      square_root(4.5)
      assert False
  except TypeError:
      assert True
output: def square_root(x):
      if not isinstance(x, int):
          raise TypeError('Input must be an integer')
      return x**0.5