Add docstrings and validation, slight refactor
Add docstrings and validation, slight refactor

kelle/astropy,dhomeier/astropy,funbaker/astropy,saimn/astropy,pllim/astropy,stargaser/astropy,tbabej/astropy,lpsinger/astropy,AustereCuriosity/astropy,larrybradley/astropy,dhomeier/astropy,DougBurke/astropy,StuartLittlefair/astropy,stargaser/astropy,tbabej/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,DougBurke/astropy,kelle/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,tbabej/astropy,bsipocz/astropy,pllim/astropy,aleksandr-bakanov/astropy,kelle/astropy,lpsinger/astropy,funbaker/astropy,joergdietrich/astropy,saimn/astropy,aleksandr-bakanov/astropy,tbabej/astropy,bsipocz/astropy,MSeifert04/astropy,AustereCuriosity/astropy,funbaker/astropy,larrybradley/astropy,MSeifert04/astropy,mhvk/astropy,pllim/astropy,saimn/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,joergdietrich/astropy,AustereCuriosity/astropy,MSeifert04/astropy,joergdietrich/astropy,kelle/astropy,dhomeier/astropy,funbaker/astropy,lpsinger/astropy,larrybradley/astropy,astropy/astropy,astropy/astropy,mhvk/astropy,DougBurke/astropy,joergdietrich/astropy,bsipocz/astropy,astropy/astropy,DougBurke/astropy,saimn/astropy,AustereCuriosity/astropy,lpsinger/astropy,tbabej/astropy,saimn/astropy,larrybradley/astropy,mhvk/astropy,MSeifert04/astropy,stargaser/astropy,mhvk/astropy,pllim/astropy,larrybradley/astropy,dhomeier/astropy,mhvk/astropy,kelle/astropy,astropy/astropy,stargaser/astropy,AustereCuriosity/astropy,lpsinger/astropy,astropy/astropy,pllim/astropy