$2.$ Activity Class $($Base Class$)$ Serves as the base class for user activities. Contains common attributes like

the user associated with the activity and the content of the activity. Both Post and Message classes

inherit from Activity.

Variables:

user $($User$)$: The user associated with the activity.

content $($str$)$: Content of the activity.

Methods:

$\_\_$init$\_\_($self$,$ user, content$)$: Initialize an Activity instance.

$\_\_$str$\_\_($self$)$: Return a string representation of the Activity.

$3.$ Post Class $($Derived from Activity$)$ Represents a user's post in the social network. Inherits from the

Activity class.

Additional Attributes:

None

Additional Methods:

$\_\_$str$\_\_($self$)$: Return a string representation of the Post.

$4.$ Message Class $($Derived from Activity$)$ Represents a user's message to another user. Inherits from the

Activity class.

Additional Attributes:

receiver $($User$)$: The user receiving the message.

Additional Methods:

Methods:

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$\_\_$str$\_\_($self$)$: Return a string representation of the Message.

$5.$ User Class Represents a user in the social network. Contains a Profile instance representing the user's

details $($username$,$ password, screen name, email$).$ Manages user activities such as creating posts and

sending messages.

Attributes:

profile $($Profile$)$: User's profile.

posts $($list of Post$)$: List of posts created by the user.

messages $($list of Message$)$: List of messages sent by the user.

Methods:

$\_\_$init$\_\_($self$,$ username, password, screen$\_$name, email$)$: Initialize a User

instance.

create$\_$post$($self$,$ content$)->$ Post: Create a new post for the user. Raise

ValueError if the content of the post is empty.

send$\_$message$($self$,$ receiver, content$)->$ Message: Send a message to another

user. Raise ValueError if the receiver ID or message content is empty.

$\_\_$str$\_\_($self$)$: Return a string representation of the User.