input: Write a python function to verify the user by connecting to a MySQL database.
  assert login_user('valid_user', 'valid_pass') == True
  assert login_user('invalid_user', 'invalid_pass') == False
  assert login_user('valid_user', 'invalid_pass') == False
output: import mysql.connector
  
  def login_user(username, password):
      try:
          conn = mysql.connector.connect(
              host="your_host",
              user="your_username",
              password="your_password",
              database="your_database"
          )
          cursor = conn.cursor()
          query = "SELECT COUNT(*) FROM users WHERE username=%s AND password=%s"
          cursor.execute(query, (username, password))
          result = cursor.fetchone()[0]
          cursor.close()
          conn.close()
          return result == 1
      except mysql.connector.Error as err:
          print(f"Error: {err}")
          return False