Add TrainFastText utility to aggregate links to training functions

Change-Id: Iadf598d930dca954ee1a0f450012cd4b4b2baab5

extensions/fasttext/README.md

@@ -5,8 +5,10 @@
 This module contains the NLP support with fastText implementation.
 
 fastText module's implementation in DJL is not considered as an Engine, it doesn't support Trainer and Predictor.
-The training and inference functionality is directly provided through [FtModel](https://javadoc.io/doc/ai.djl.fasttext/fasttext-engine/latest/ai/djl/fasttext/FtModel.html)
-class. You can find examples [here](https://github.com/deepjavalibrary/djl/blob/master/extensions/fasttext/src/test/java/ai/djl/fasttext/CookingStackExchangeTest.java).
+Training is only supported by using [TrainFastText](https://javadoc.io/doc/ai.djl.fasttext/fasttext-engine/latest/ai/djl/fasttext/TrainFastText.html).
+This produces a special block which can perform inference on its own or by using a model and predictor.
+Pre-trained FastText models can also be loaded by using the standard DJL criteria.
+You can find examples [here](https://github.com/deepjavalibrary/djl/blob/master/extensions/fasttext/src/test/java/ai/djl/fasttext/CookingStackExchangeTest.java).
 
 Current implementation has the following limitations:
 

extensions/fasttext/src/main/java/ai/djl/fasttext/FtModel.java

@@ -41,7 +41,8 @@
 /**
  * {@code FtModel} is the fastText implementation of {@link Model}.
  *
- * <p>FtModel contains all the methods in Model to load and process a model.
+ * <p>FtModel contains all the methods in Model to load and process a model. However, it only
+ * supports training by using {@link TrainFastText}.
  */
 public class FtModel implements Model {
 

extensions/fasttext/src/main/java/ai/djl/fasttext/TrainFastText.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
+ * OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
+ * and limitations under the License.
+ */
+package ai.djl.fasttext;
+
+import ai.djl.basicdataset.RawDataset;
+import ai.djl.fasttext.zoo.nlp.textclassification.FtTextClassification;
+import java.io.IOException;
+import java.nio.file.Path;
+
+/** A utility to aggregate options for training with fasttext. */
+public final class TrainFastText {
+
+    private TrainFastText() {}
+
+    /**
+     * Trains a fastText {@link ai.djl.Application.NLP#TEXT_CLASSIFICATION} model.
+     *
+     * @param config the training configuration to use
+     * @param dataset the training dataset
+     * @return the result of the training
+     * @throws IOException when IO operation fails in loading a resource
+     * @see FtTextClassification#fit(FtTrainingConfig, RawDataset)
+     */
+    public static FtTextClassification textClassification(
+            FtTrainingConfig config, RawDataset<Path> dataset) throws IOException {
+        return FtTextClassification.fit(config, dataset);
+    }
+}

extensions/fasttext/src/test/java/ai/djl/fasttext/CookingStackExchangeTest.java

@@ -66,7 +66,7 @@ public void testTrainTextClassification() throws IOException, TranslateException
                         .optLoss(FtTrainingConfig.FtLoss.HS)
                         .build();
 
-        FtTextClassification block = FtTextClassification.fit(config, dataset);
+        FtTextClassification block = TrainFastText.textClassification(config, dataset);
         TrainingResult result = block.getTrainingResult();
         Assert.assertEquals(result.getEpoch(), 5);
         Assert.assertTrue(Files.exists(Paths.get("build/cooking.bin")));