Returns true if the given collection or string is empty.
Returns true of the given argument is null, returns false for any other non-collection, non-string argument.
empty? [] # --> true
empty? {} # --> true
empty? '' # --> true
empty? null # --> true
empty? [ 1, 2, 3 ] # --> false
empty? { a: 'A' } # --> false
empty? 0 # --> false
empty? 'aaa' # --> false
If the argument is not an array, an object, a string or null, an error is triggered.
If there is no argument to the "empty?", the incoming payload['ret'] is considered
{}
empty? _ # --> true
[ 1, 2, 3 ]
empty? _ # --> false