This class represent an instance of a constraint.
In general, all AMPL suffixes for a constraint are available through methods
with the same name in this class. See https://www.ampl.com/NEW/suffbuiltin.html
for a list of the available suffixes.
Note that, since this class represents instances of both algebraic and logical
constraints, some suffixes might not be available for every instance.
If a wrong suffix for the specific class
of constraint is accessed, an error is thrown.
All the accessors in this class throw an error if the instance
has been deleted in the underlying AMPL interpreter.