@Override
        public Function<T, A> firstStep() {
            return before;
        }
Internal implementation of the {@link ComposedExpression}. Booleans are
handled a bit differently when it comes to {@code null}-values. If the
{@code before}-function returns {@code null}, then the expression will
always evaluate to {@code false}. This is to stay compatible with how
Speedment handles predicates in streams.

@param <T>      the outer input type
@param <A>      the inner input type
@param <AFTER>  the expression type of the {@code after} operation
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/internal/expression/ComposedUtil.java