Purpose: Checks whether a value is of type object. The value can be of any type but must be declared in case of a variable or object field.

Return Values: Returns true if and only if value is of type object, otherwise false.

Example:

heitml input:	resulting output:
<? istuple(emptytuple)>	true
<? istuple(true)>	false
<? istuple(1)>	false
<? istuple(null)>	false