input: Write a python function to connect to a MySQL database and execute a query using MySQL Connector/Python.
  assert execute_query("SELECT DATABASE();") == [("test_db",)]
  assert execute_query("SELECT 1;") == [(1,)]
  assert execute_query("SELECT COUNT(*) FROM users;") == [(5,)]
output: def execute_query(query):
      import mysql.connector
      from mysql.connector import Error
  
      try:
          # Establish the connection
          connection = mysql.connector.connect(
              host='localhost',
              database='test_db',
              user='your_username',
              password='your_password'
          )
  
          if connection.is_connected():
              cursor = connection.cursor()
              cursor.execute(query)
              result = cursor.fetchall()
              return result
  
      except Error as e:
          print(f"Error: {e}")
      finally:
          if connection.is_connected():
              cursor.close()
              connection.close()