code: function checkBinaryReady(uuid) {
        if (!(uuid in api._blobs && uuid in api._binaryMessages)) {
          return;
        }
        log('receive full binary message', uuid);
        var blob = api._blobs[uuid];
        var msg = api._binaryMessages[uuid];
  
        delete api._blobs[uuid];
        delete api._binaryMessages[uuid];
  
        var blobToDeliver;
        if (isBrowser) {
          blobToDeliver = blobUtil.createBlob([blob], {type: msg.contentType});
        } else {
          blobToDeliver = blob;
          blob.type = msg.contentType; // non-standard, but we do it for the tests
        }
  
        msg.cb(null, blobToDeliver);
      }
docs: binary messages come in two parts; wait until we've received both