get User Followers
Get follower list of given user
Return
Flow of usernames/userids
Parameters
amountOfFollowers
Amount of follower users to retrieve
isUsername
Whether to retrieve username of follower or not (if false, userid will be returned)
isFilterPrivate
Whether to filter private account or not
isFilterVerified
Whether to filter verified account or not
fileNameToWrite
File name to write usernames of follower list. This is especially useful when follower list is large (> 10K)
isOverwrite
Whether to replace existing usernames file or not