DOC: Add docstring to avoid Sphinx warning
DOC: Add docstring to avoid Sphinx warning

astropy/astropy,StuartLittlefair/astropy,saimn/astropy,dhomeier/astropy,dhomeier/astropy,pllim/astropy,saimn/astropy,astropy/astropy,lpsinger/astropy,mhvk/astropy,mhvk/astropy,pllim/astropy,saimn/astropy,pllim/astropy,larrybradley/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,StuartLittlefair/astropy,pllim/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,dhomeier/astropy,mhvk/astropy,saimn/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,mhvk/astropy,pllim/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,dhomeier/astropy,dhomeier/astropy,lpsinger/astropy,StuartLittlefair/astropy,lpsinger/astropy,astropy/astropy,larrybradley/astropy,astropy/astropy,larrybradley/astropy,mhvk/astropy,larrybradley/astropy,astropy/astropy,saimn/astropy