DOC: fix docstring validation errors for pandas.Series.dt.freq (#60377)

* Added docs for Series.dt.freq and removed from ci/code_checks.sh

* Fix code style

Author: Ivruix

ci/code_checks.sh

@@ -73,7 +73,6 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
         -i "pandas.Period.freq GL08" \
         -i "pandas.Period.ordinal GL08" \
         -i "pandas.RangeIndex.from_range PR01,SA01" \
-        -i "pandas.Series.dt.freq GL08" \
         -i "pandas.Series.dt.unit GL08" \
         -i "pandas.Series.pad PR01,SA01" \
         -i "pandas.Timedelta.max PR02" \

pandas/core/indexes/accessors.py

@@ -373,6 +373,28 @@ def to_pydatetime(self) -> Series:
 
     @property
     def freq(self):
+        """
+        Tries to return a string representing a frequency generated by infer_freq.
+
+        Returns None if it can't autodetect the frequency.
+
+        See Also
+        --------
+        Series.dt.to_period : Cast to PeriodArray/PeriodIndex at a particular
+            frequency.
+
+        Examples
+        --------
+        >>> ser = pd.Series(["2024-01-01", "2024-01-02", "2024-01-03", "2024-01-04"])
+        >>> ser = pd.to_datetime(ser)
+        >>> ser.dt.freq
+        'D'
+
+        >>> ser = pd.Series(["2022-01-01", "2024-01-01", "2026-01-01", "2028-01-01"])
+        >>> ser = pd.to_datetime(ser)
+        >>> ser.dt.freq
+        '2YS-JAN'
+        """
         return self._get_values().inferred_freq
 
     def isocalendar(self) -> DataFrame: