input: Write a python function to connect to a MySQL database using mysql.connector and return the connection object.
  assert isinstance(connect_to_database(), mysql.connector.connection.MySQLConnection)
output: def connect_to_database():
      import mysql.connector
      from mysql.connector import Error
  
      try:
          connection = mysql.connector.connect(
              host='your_host',
              user='your_user',
              password='your_password',
              database='your_database'
          )
          if connection.is_connected():
              return connection
      except Error as e:
          print(f"Error: {e}")
          return None