Return the constraint list for the adapter. A Unary node in the Ptolemy
expression language is a node with a single child node and an operator that
is either a negation (-), a logical not (!), or a bitwise not (~). This
ontology constraint supports using the concept functions for the negation and
logical not operations if they are defined in the LatticeOntologySolver's model.
If the concept functions are not defined or the operation is bitwise not, then
the constraint is just between the node and its child node.