Determines whether the set contains the element, provided as an IElement or string or integer label.
Returns true if this set contains the specified IElement.
virtual bool contains(const IElement* element) const = 0;
Returns true if this set contains the specified label. Does not apply to subsets of Integers.
virtual bool contains(const char* label) const = 0;
Returns true if this set contains the specified label. Applies to subsets of Integers.
virtual bool contains(int label) const = 0;
