ValueError: Unable to coerce to Series, length must be 1: given 2854

[wasifmasood]

Hi,
I have found your approach to mixed effects modeling very appealing and therefore wanted to try my data which is about network traffic prediction, a very valuable and in demand use case. But unfortunately, I am encoutering the following error with full stack trace, can you please help me in finding the source of the problem:

ValueError                                Traceback (most recent call last)
<ipython-input-293-b5c7b2f082a6> in <module>
      1 mrf = MERF(max_iterations=500)
----> 2 mrf.fit(X_train_merf, Z_train, clusters_train, y_train)

C:\ProgramData\Anaconda3\envs\shared\lib\site-packages\merf\merf.py in fit(self, X, Z, clusters, y, X_val, Z_val, clusters_val, y_val)
    209 
    210                 # Compute y_star for this cluster and put back in right place
--> 211                 y_star_i = y_i - Z_i.dot(b_hat_i)
    212                 y_star[indices_i] = y_star_i
    213 

C:\ProgramData\Anaconda3\envs\shared\lib\site-packages\pandas\core\ops\__init__.py in f(self, other, axis, level, fill_value)
    645         # TODO: why are we passing flex=True instead of flex=not special?
    646         #  15 tests fail if we pass flex=not special instead
--> 647         self, other = _align_method_FRAME(self, other, axis, flex=True, level=level)
    648 
    649         if isinstance(other, ABCDataFrame):

C:\ProgramData\Anaconda3\envs\shared\lib\site-packages\pandas\core\ops\__init__.py in _align_method_FRAME(left, right, axis, flex, level)
    472 
    473         if right.ndim == 1:
--> 474             right = to_series(right)
    475 
    476         elif right.ndim == 2:

C:\ProgramData\Anaconda3\envs\shared\lib\site-packages\pandas\core\ops\__init__.py in to_series(right)
    463         else:
    464             if len(left.columns) != len(right):
--> 465                 raise ValueError(
    466                     msg.format(req_len=len(left.columns), given_len=len(right))
    467                 )

ValueError: Unable to coerce to Series, length must be 1: given 2854

Here is the my git repo where you can find the complete example
https://github.com/wasifmasood/network_traffic_forecast/blob/master/MERF.ipynb