Facing error in completing the protein ligand binding tutorial

Hello guys,

I was doing a tutorial of “Modeling_Protein_Ligand_Interactions_With_Atomic_Convolutions”
I was running a notebook in colab.

for the code block
max_epochs = 50

metric = dc.metrics.Metric(dc.metrics.score_function.rms_score)
step_cutoff = len(train)//12
def val_cb(model, step):
  if step%step_cutoff!=0:
  val_losses.append(model.evaluate(val, metrics=[metric])['rms_score']**2)  # L2 Loss
  losses.append(model.evaluate(train, metrics=[metric])['rms_score']**2)  # L2 Loss

acm.fit(train, nb_epoch=max_epochs, max_checkpoints_to_keep=1,

I am getting error:
ValueError: could not broadcast input array from shape (154,) into shape (1,)

kindly help me resolve this issue.