input: Write a function to encrypt a given string by shifting each character by 2 ASCII values.
  assert encrypt_string("python") == "ravjqp"
  assert encrypt_string("hello") == "jgnnq"
  assert encrypt_string("abc") == "cde"
output: def encrypt_string(s):
      return ''.join(chr(ord(char) + 2) for char in s)