KNNMemory add() does not appear to update self.knns

[vyaivo]

Thanks for the nice implementation. I've adapted this code for my own use, so I don't have the whole stack that would reproduce this bug. However, you can check for yourself.

The following code ought to update the KNN objects in the KNNMemory class:

@delayed
def knn_add(knn, key, db_offset):
    knn.add(key, ids = knn_insert_ids + db_offset)

Parallel(n_jobs = self.n_jobs)(knn_add(*args) for args in zip(knns, keys, db_offsets))

[link to that code here]

However, even after repeated calls to add to the memory, calling KNNMemory.search() results in empty values. If you view self.knns at this point, self.is_trained remains False.

When I modify the code as follows, this fixes the issue.

@delayed
def knn_add(knn, key, db_offset):
    knn.add(key, ids = knn_insert_ids + db_offset)
    return knn

updated_knns = Parallel(n_jobs = self.n_jobs)(knn_add(*args) for args in zip(knns, keys, db_offsets))
self.knns = updated_knns

This will allow searches to return actual values.