validateHazardousMaterialsCode function
Validates Hazardous Materials Code.
Returns null if valid, or an error message string if invalid.
Implementation
String? validateHazardousMaterialsCode(String? value) {
if (value == null || value.isEmpty) {
return 'Please enter a hazardous materials code';
}
// Hazardous materials codes vary; adjust validation as needed.
return null;
}