question: public CheckpointManager ( NetworkParameters params , @ Nullable InputStream inputStream ) throws IOException { this . params = checkNotNull ( params ) ; if ( inputStream == null ) inputStream = openStream ( params ) ; checkNotNull ( inputStream ) ; inputStream = new BufferedInputStream ( inputStream ) ; inputStream . mark ( 1 ) ; int first = inputStream . read ( ) ; inputStream . reset ( ) ; if ( first == BINARY_MAGIC . charAt ( 0 ) ) dataHash = readBinary ( inputStream ) ; else if ( first == TEXTUAL_MAGIC . charAt ( 0 ) ) dataHash = readTextual ( inputStream ) ; else throw new IOException ( "Unsupported format." ) ; }
target:  Loads the checkpoints from the given stream 