DOC: fixing RT03 erros for Index: duplicated and nunique (#58432)

* DOC: fixing RT03 erros for Index: duplicated and nunique

* deleting it lines from code_checks

* fixing EXPECTED TO FAIL, BUT NOT FAILING error

* fixing code_checks issue

* fixed Expected to fail error

Author: KeiOshima

ci/code_checks.sh

@@ -93,15 +93,13 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
         -i "pandas.Index PR07" \
         -i "pandas.Index.append PR07,RT03,SA01" \
         -i "pandas.Index.difference PR07,RT03,SA01" \
-        -i "pandas.Index.duplicated RT03" \
         -i "pandas.Index.get_indexer PR07,SA01" \
         -i "pandas.Index.get_indexer_for PR01,SA01" \
         -i "pandas.Index.get_indexer_non_unique PR07,SA01" \
         -i "pandas.Index.get_loc PR07,RT03,SA01" \
         -i "pandas.Index.identical PR01,SA01" \
         -i "pandas.Index.join PR07,RT03,SA01" \
         -i "pandas.Index.names GL08" \
-        -i "pandas.Index.nunique RT03" \
         -i "pandas.Index.putmask PR01,RT03" \
         -i "pandas.Index.ravel PR01,RT03" \
         -i "pandas.Index.slice_indexer PR07,RT03,SA01" \
@@ -256,7 +254,6 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
         -i "pandas.Series.mode SA01" \
         -i "pandas.Series.mul PR07" \
         -i "pandas.Series.ne PR07,SA01" \
-        -i "pandas.Series.nunique RT03" \
         -i "pandas.Series.pad PR01,SA01" \
         -i "pandas.Series.plot PR02,SA01" \
         -i "pandas.Series.pop RT03,SA01" \

pandas/core/base.py

@@ -1062,6 +1062,7 @@ def nunique(self, dropna: bool = True) -> int:
         Returns
         -------
         int
+            A integer indicating the number of unique elements in the object.
 
         See Also
         --------

pandas/core/indexes/base.py

@@ -2767,6 +2767,7 @@ def duplicated(self, keep: DropKeep = "first") -> npt.NDArray[np.bool_]:
         Returns
         -------
         np.ndarray[bool]
+            A numpy array of boolean values indicating duplicate index values.
 
         See Also
         --------