Returns a string value representation for the element.

Note: When called on an element driven by relations, the function will return the first appropriate relations string involving this element value. The relation string should be used only to identify that the element is driven by relations, and should not be used to calculate the element value. This is because the element value may be driven by more than one relation simultaneously in the feature's relation set. Refer to ProRelSet.h for more details about relations and relation sets.