added docstring and comments to two fns
added docstring and comments to two fns

Carralex/landlab,ManuSchmi88/landlab,laijingtao/landlab,Carralex/landlab,landlab/landlab,cmshobe/landlab,ManuSchmi88/landlab,RondaStrauch/landlab,SiccarPoint/landlab,landlab/landlab,Carralex/landlab,decvalts/landlab,cmshobe/landlab,SiccarPoint/landlab,ManuSchmi88/landlab,landlab/landlab,cmshobe/landlab,amandersillinois/landlab,laijingtao/landlab,csherwood-usgs/landlab,decvalts/landlab,RondaStrauch/landlab,amandersillinois/landlab,RondaStrauch/landlab,csherwood-usgs/landlab