Mention Reducer's primary methods.

A Reducer's primary methods are:

Setup(): this is a method that is only used to set up the reducer's various arguments

Reduce: The primary function of the reducer is reduce(). This method's specific purpose is to specify the task that needs to be completed for each unique group of values that share a key.

Cleanup: After completing the reduce() task, cleaning() is used to clean up or destroy any temporary files or data.