Minor issues in tldr tutorial

[BioinfoTongLI]

Hello there,

Thanks for this great tool!
I am trying to reproduce the results in tldr page and encoutered two minor issues.
Would you please help on this?

1. the variable output_mask is not defined in the analysis.filter_celltypemaps
2. the variable scrna_colors is not defined in the ds.plot_celltypes_map

Many thanks for your help!

Best,

Tong