added docstring for Bin
added docstring for Bin

sdss/marvin,albireox/marvin,albireox/marvin,bretthandrews/marvin,albireox/marvin,sdss/marvin,sdss/marvin,bretthandrews/marvin,bretthandrews/marvin,bretthandrews/marvin,albireox/marvin,sdss/marvin