Seperating big vectors into chunks

[Cem-Gulec]

** How error looks like? **
Error: cannot allocate vector of size 9.8 Gb

Is your feature request related to a problem? Please describe.
Specifically for the datasets of heart and lung, it is not really possible to process them without big hardware recources - which is not really efficient.

Describe the solution you'd like
For each cell type in the matrix, μ and r values (gamma mixed fits) can be extracted and could progress from there on. Also see anndata, might help on reading for an alternative solution

[Cem-Gulec]

fixed by 84286e4