As far as I know
Definition 1 of 1
Pro Tip 1/3Uncertainty Expression
Indicates you are not completely sure about the information you are providing, but you believe it to be true based on what you know. 
As far as I know, the meeting is at 2 PM.
Pro Tip 2/3Non-Commitment
Allows you to share information without fully committing to its accuracy, providing a level of protection if the information is incorrect. 
As far as I know, the tickets are sold out.
Pro Tip 3/3Conversation Softener
Softens the tone of a conversation when you're correcting someone or contradicting information they have given. 
As far as I know, the homework is due next week, not this Friday.