code: public static Transaction fromProposal(Proposal prop) {
      Zxid zxid = fromProtoZxid(prop.getZxid());
      ByteBuffer buffer = prop.getBody().asReadOnlyByteBuffer();
      return new Transaction(zxid, prop.getType().getNumber(), buffer);
    }
docs: Converts protobuf Proposal object to Transaction object.
  
  @param prop the protobuf Proposal object.
  @return the Transaction object.