DOCS-modin-project#4469: Say that commit messages can start with PERF.

Signed-off-by: mvashishtha <[email protected]>

docs/development/contributing.rst

@@ -101,6 +101,7 @@ message can be one of the following:
 * FIX: A bugfix contribution
 * REFACTOR: Moving or removing code without change in functionality
 * TEST: Test updates or improvements
+* PERF: Performance enhancements
 
 The ``#9999`` component of the commit message should be the issue number in the Modin
 GitHub issue tracker: https://github.com/modin-project/modin/issues. This is important

modin/pandas/test/dataframe/test_map_metadata.py

@@ -11,6 +11,7 @@
 # ANY KIND, either express or implied. See the License for the specific language
 # governing permissions and limitations under the License.
 
+from re import I
 import pytest
 import numpy as np
 import pandas
@@ -746,9 +747,15 @@ def test_droplevel():
     [None, "col1", "name", ("col1", "col3"), ["col1", "col3", "col7"]],
     ids=["None", "string", "name", "tuple", "list"],
 )
-def test_drop_duplicates(data, keep, subset):
-    modin_df = pd.DataFrame(data)
-    pandas_df = pandas.DataFrame(data)
+@pytest.mark.parametrize("all_rows_have_label_zero", [True, False])
+def test_drop_duplicates(data, keep, subset, all_rows_have_label_zero):
+
+    if all_rows_have_label_zero:
+        columns = [0] * len(data[next(iter(data))])
+    else:
+        columns = None
+    modin_df = pd.DataFrame(data, columns=columns)
+    pandas_df = pandas.DataFrame(data, columns=columns)
 
     try:
         pandas_df.drop_duplicates(keep=keep, inplace=False, subset=subset)