label method
Attaches a system-wide label to the specified unit.
If the specified label is already associated to an unit the previous association is discarded or ignored.
Implementation
void label(Unit unit, String label) {
if (!isValidIdentifier(label)) {
throw ArgumentError('Label: $label is not a valid identifier.');
}
_nameToUnit[label] = unit;
_unitToName[unit] = label;
}