A decision variable instance. Each member of this class belongs to a single
Note that accessors available here are replicated at Variable level for ease
of use when dealing with scalar variables.
All AMPL suffixes for an algebraic variable 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.
All the accessors in this class throw an error if the instance
has been deleted in the underlying AMPL interpreter.