Notification System with Error Validation

class NotificationClient:
    """
    A notification client that sends notifications with proper error handling.
    """

    def __init__(self, hostname='localhost', port=23053, password=None):
        """
        Initialize the notification client.

        Args:
            hostname: The server hostname
            port: The server port
            password: Optional password for authentication
        """
        pass

    def register(self, app_name, notification_types):
        """
        Register the application with the server.

        Args:
            app_name: Name of the application
            notification_types: List of notification type names to register

        Raises:
            ConnectionError: If unable to connect to the server
            ValueError: If the server response is invalid
            AuthenticationError: If authentication fails
        """
        pass

    def send_notification(self, notification_type, title, description=''):
        """
        Send a notification to the server.

        Args:
            notification_type: The type of notification (must be registered)
            title: Notification title
            description: Optional notification description

        Raises:
            ConnectionError: If unable to connect to the server
            ValueError: If the server response is invalid or notification type not registered
            AuthenticationError: If authentication fails
        """
        pass

class AuthenticationError(Exception):
    """Raised when authentication with the server fails."""
    pass