Sample-based pipelines inefficiencies

This is a generic issue that I am raising that I believe we will face moving forward. The biggest issue that I have found with our sample-based approach is when you have to concatenate samples to make a big array for processing steps such as .fit methods. The reason for this is that we are looking at samples individually, even though they might have come from a bigger array. Let me demonstrate this with an example: sample_stacking_issue.html or sample_stacking_issue.ipynb