Requires that the inputs are the same size.
Raises an error if the inputs a and b are not the same size,
as determined by
isequal (size (a), size (b)).
labelA and labelB are optional inputs that determine how
the input will be described in error messages. If not supplied,
inputname (...) is used, and if that is empty, it falls back to
"input 1" and "input 2".