[skip ci] Add comments of benchmark (#11096)

Signed-off-by: Nwangting0128 <ting.wang@zilliz.com>

tests/benchmark/milvus_benchmark/runners/utils.py

@@ -138,6 +138,7 @@ def metric_type_trans(metric_type):
 
 
 def get_dataset(hdf5_file_path):
+    """ Determine whether hdf5 file exists, and return the content of hdf5 file """
     if not os.path.exists(hdf5_file_path):
         raise Exception("%s not existed" % hdf5_file_path)
     dataset = h5py.File(hdf5_file_path)