@Override
    default Class<Table> mainInterface() {
        return Table.class;
    }
Locate the {@link PrimaryKeyColumn} child with the specified id if it
exists, else return an empty {@code Optional}.

@param id  the {@link HasId#getId()} of the primary key column
@return    the child found or an empty {@code Optional}
runtime-parent/runtime-config/src/main/java/com/speedment/runtime/config/Table.java