'burn' is working only in cli mode

[robert-werner]

When I use supermercado burn in cli mode, it works, passing [x,y,z]'s to specified file. When I use it as Python function, it does not work, writing this:
File "C:\Users\someuser\Anaconda3\envs\somecode\lib\site-packages\supermercado\burntiles.py", line 20, in find_extrema totalArr = np.array([c for f in features for poly in f['geometry']['coordinates'] for c in poly for poly in f]) File "C:\Users\someuser\Anaconda3\envs\somecode\lib\site-packages\supermercado\burntiles.py", line 20, in <listcomp> totalArr = np.array([c for f in features for poly in f['geometry']['coordinates'] for c in poly for poly in f]) TypeError: string indices must be integers