@Override
    public Struct validate(Object item) {
        try {
            Struct struct = (Struct) item;
            for (BoundField field : fields) {
                try {
                    field.def.type.validate(struct.get(field));
                } catch (SchemaException e) {
                    throw new SchemaException("Invalid value for field '" + field.def.name + "': " + e.getMessage());
                }
            }
            return struct;
        } catch (ClassCastException e) {
            throw new SchemaException("Not a Struct.");
        }
    }
Display a string representation of the schema
clients/src/main/java/org/apache/kafka/common/protocol/types/Schema.java