This method is identical to the addString() method but here a separator is also included.
Method Definition: def addString(b: StringBuilder, sep: String): StringBuilder
Where, sep is the separator stated.
Return Type: It returns the elements of the map in the String Builder and a separator is also added between the elements of the map.
geeks -> 5_for -> 3_cs -> 2
geeks -> 2_for -> 3
So, here the identical keys are removed.