Add _get_key function
Add _get_key function

jakirkham/dask,dask/dask,blaze/dask,cpcloud/dask,mrocklin/dask,wiso/dask,freeman-lab/dask,jcrist/dask,jayhetee/dask,freeman-lab/dask,ssanderson/dask,clarkfitzg/dask,pombredanne/dask,mraspaud/dask,gameduell/dask,vikhyat/dask,clarkfitzg/dask,mraspaud/dask,simudream/dask,ssanderson/dask,PhE/dask,jakirkham/dask,jcrist/dask,dask/dask,ContinuumIO/dask,chrisbarber/dask,simudream/dask,jayhetee/dask,wiso/dask,pombredanne/dask,ContinuumIO/dask,PhE/dask,vikhyat/dask,blaze/dask,mikegraham/dask,mrocklin/dask,cowlicks/dask