Update README and release YAML to reflect python 3.9 support (#658)

* Update README and release YAML to reflect python 3.9 support

* Fix lint error

.github/workflows/release.yaml

@@ -191,7 +191,7 @@ jobs:
       - name: Set up python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with:
-          python-version: 3.7
+          python-version: 3.9
 
       - name: Set version
         run: make set-version

README.md

@@ -37,7 +37,7 @@ The library was developed by Iguazio to simplify working with data in the [Iguaz
 <a id="python-version"></a>
 #### Python Version
 
-The current version of Frames supports Python 3.6 and 3.7.
+The current version of Frames supports Python 3.7 and 3.9.
 
 <a id="initialization"></a>
 #### Initialization

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]