001/*
002 * Copyright (c) 2015-2020, Oracle and/or its affiliates. All rights reserved.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.tribuo.classification.sequence.viterbi;
018
019import com.oracle.labs.mlrg.olcut.provenance.ConfiguredObjectProvenance;
020import com.oracle.labs.mlrg.olcut.provenance.impl.ConfiguredObjectProvenanceImpl;
021import org.tribuo.Feature;
022import org.tribuo.classification.Label;
023
024import java.util.Collections;
025import java.util.List;
026
027/**
028 * A label feature extractor that doesn't produce any label based features.
029 * <p>
030 * It always returns {@link Collections#emptyList()}.
031 */
032public class NoopFeatureExtractor implements LabelFeatureExtractor {
033
034    private static final long serialVersionUID = 1L;
035
036    @Override
037    public List<Feature> extractFeatures(List<Label> previousOutcomes, double value) {
038        return Collections.emptyList();
039    }
040
041    @Override
042    public String toString() {
043        return "NoopFeatureExtractor";
044    }
045
046    @Override
047    public ConfiguredObjectProvenance getProvenance() {
048        return new ConfiguredObjectProvenanceImpl(this, "LabelFeatureExtractor");
049    }
050}
051