code: public LREnvelope sign(LREnvelope envelope) throws LRException
      {
          // Bencode the document
          String bencodedMessage = bencode(envelope.getSignableData());
  
          // Clear sign the bencoded document
          String clearSignedMessage = signEnvelopeData(bencodedMessage);
  
          envelope.addSigningData(signingMethod, publicKeyLocation, clearSignedMessage);
  
          return envelope;
      }
docs: Sign the specified envelope with this signer
  
  @param envelope envelope to be signed
  @return signed envelope
  @throws LRException