doc added

git-svn-id: file:///humgen/gsa-scr1/gsa-engineering/svn_contents/trunk@464 348d0f76-0448-11de-a6fe-93d51630548a

java/src/org/broadinstitute/sting/gatk/walkers/ReadWalker.java

@@ -14,6 +14,9 @@ public abstract class ReadWalker<MapType, ReduceType> extends Walker<MapType, Re
     public boolean requiresOrderedReads() { return false; }
     
     // Do we actually want to operate on the context?
+    /** Must return true for reads that need to be processed. Reads, for which this method return false will
+     * be skipped by the engine and never passed to the walker.
+     */
     public boolean filter(LocusContext context, SAMRecord read) {
         // We are keeping all the reads
         return true;