why this private Stream<FieldValidator<ProductPipoDTO>> smartClientFunctionalities() {
        return Stream.of(
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("fpcRefCodes"))
                                .errorMsg("Ref. FPC NAME_1 should contain digits only. Temporary NAME_1 cannot be used as a reference.")
                                .expression("^((([0-9]{8,10})\\s*[,]?\\s*))*$")
                                .function(ProductPipoDTO::getFpcRefCodes),
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("piFpcCode"))
                                .errorMsg("FPC NAME_1 should contain digits only, or temporary FPC NAME_1")
                                .expression("(FPC[0-9]*$)|(^[0-9]*$)")
                                .function(ProductPipoDTO::getPiFpcCode),
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("poFpcCode"))
                                .errorMsg("FPC NAME_1 should contain digits only, or temporary FPC NAME_1")
                                .expression("(FPC[0-9]*$)|(^[0-9]*$)")
                                .function(ProductPipoDTO::getPoFpcCode),
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("unitSizeAsSourced"))
                                .errorMsg("Size should be a number")
                                .expression(sizeValidatorRegexp())
                                .function(ProductPipoDTO::getUnitSizeAsSourced),
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("unitSizeMetric"))
                                .errorMsg("Size should be a number")
                                .expression(sizeValidatorRegexp())
                                .function(ProductPipoDTO::getUnitSizeMetric),
                        ScopeIndependentRegexProvider.<ProductPipoDTO>builder()
                                .fieldCode(FieldCode.of("piFpcDescription"))
                                .errorMsg("Invalid characters. Only following characters are allowed: a-z A-Z 0-9 ! % & ( ) * + / ; < = > ^ . - _ 'tilde'")
                                .javaExpression("^([^\\u0000-\\u001F\\u007F\\u00C0-\\uDBFF\\uDFFF,:\\[\\]\\{\\}|\\$#\\\\?\"'£])*$")
                      