Fix lint error

clients/py/v3io_frames/pbutils.py

@@ -183,7 +183,7 @@ def df2msg(df, labels=None, index_cols=None):
     indices = None
     if index_cols is not None:
         # if there is already an index set, we want to preserve it.
-        if not (type(df.index) == pd.RangeIndex and df.index.name is None):
+        if not (isinstance(df.index, pd.RangeIndex) and df.index.name is None):
             df.reset_index(inplace=True)
         indices = [series2col(df[name], name) for name in index_cols]
         cols = [col for col in df.columns if col not in index_cols]