Update code to get a science variable for collections that have groups and no science vars in lat/lon group

[nlenssen2013]

   if lat_var_name in list(nc_d.groups[g].variables.keys()):
                group_list.append(g)
                lat_group = '/'.join(group_list)
                subsetted_ds_new = xarray.open_dataset(subsetted_filepath, group=lat_group, decode_times=False)
                # add a science variable to the dataset if other groups are in the lat/lon group
                # some GPM collections won't have any other variables in the same group as lat/lon
                if len(list(nc_d.groups[g].groups.keys())) > 0:
                    data_group = [v for v in list(nc_d.groups[g].groups.keys()) if 'time' not in str(v).lower()][0]
                    g_data = lat_group+'/'+data_group
                    subsetted_ds_data = xarray.open_dataset(subsetted_filepath, group=g_data, decode_times=False)
                    sci_var = list(subsetted_ds_data.variables.keys())[0]
                    subsetted_ds_new['science_test'] = subsetted_ds_data[sci_var]