@Override
	public Page<T> findAll(Pageable pageable) {
		Assert.isNull(pageable.getSort(), "Arbitrary sorting is not implemented");
		return slice((List<T>) findAll(), pageable);
	}
Base implementation for an in-memory store, using a {@link Map} internally.

Default behaviour is to retain sort order on the keys. Hence, this is by default the only sort supported when
querying with a {@link Pageable}.

@param <T> the type of things to store
@param <ID> a "primary key" to the things
@author Eric Bottard
spring-xd-analytics/src/main/java/org/springframework/xd/store/AbstractInMemoryRepository.java