input: Write a function to modify the given Python code to raise an 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)==2.0
  assert square_root("4")
  assert square_root(9)==3.0
  assert square_root(None)
  assert square_root(16)==4.0
output: def square_root(x):
      if not isinstance(x, int):
          raise TypeError('Input must be an integer')
      return x**0.5