TASK DEFINITION: In this task you are given a tweet. You must judge whether the author of the tweet is sad or not. Label the instances as "Sad" or "Not sad" based on your judgment. You can get help from hashtags and emojis, but you should not judge only based on them, and should pay attention to tweet's text as well.
PROBLEM: @TweeriaLee A stumbling block to the pessimist is a stepping stone to the optimist.

SOLUTION: Not sad

PROBLEM: @ArcadianLuthier -- taking out his feelings on Kei unfairly. His lips form a frown as he tries to walk away.

SOLUTION: Sad

PROBLEM: Caballero's passing remains absolutely dreadful I see!

SOLUTION:
Sad