input: Write a python function to create a connection to a MySQL database and execute a simple SELECT query.
  assert execute_query("localhost", "admin", "admin123", "test", "SELECT * FROM users") is not None
  assert execute_query("localhost", "admin", "admin123", "test", "SELECT name FROM users WHERE id=1") == [("John Doe",)]
  assert execute_query("localhost", "admin", "admin123", "test", "SELECT COUNT(*) FROM users") == [(10,)]
output: import mysql.connector
  
  def execute_query(host, user, password, database, query):
      try:
          connection = mysql.connector.connect(
              host=host,
              user=user,
              password=password,
              database=database
          )
          cursor = connection.cursor()
          cursor.execute(query)
          result = cursor.fetchall()
          return result
      except mysql.connector.Error as err:
          print(f"Error: {err}")
          return None
      finally:
          if connection.is_connected():
              cursor.close()
              connection.close()