grammar fix in convert_to_df_variable
grammar fix in convert_to_df_variable

shoyer/xray,kjordahl/xray,clarkfitzg/xray,petercable/xray,jhamman/xarray,NicWayand/xray,shoyer/xarray,rabernat/xray,xray/xray,chunweiyuan/xarray,jhamman/xarray,pydata/xarray,markelg/xray,pydata/xarray,hetland/xray,kjordahl/xray,hetland/xray,shoyer/xarray,clarkfitzg/xray,drewokane/xray,pydata/xarray,cpaulik/xray,markelg/xray,jhamman/xarray,cpaulik/xray,jcmgray/xarray,jhamman/xray,markelg/xray,rabernat/xray