input: Write a python function to encrypt a string using a password with the hashlib library.
  assert encrypt_string("Hello World!", "password") == '68e109f0f40ca72a33e8b4a399e4646f9d1a4f78e4d5e7a048c6e357ae2d2abf'
  assert encrypt_string("test", "1234") == '098f6bcd4621d373cade4e832627b4f6e99a18c428cb38d5f260853678922e03'
  assert encrypt_string("abcdef", "abcdef") == 'e80b5017098950fc58aad83c8c14978e7ac66c264f7d78ef8076b5d4abfeaeab'
output: import hashlib
  
  def encrypt_string(message, password):
      combined = message + password
      encrypted = hashlib.sha256(combined.encode()).hexdigest()
      return encrypted