DOC: add documentation to pandas.core.groupby.SeriesGroupBy.unique (pandas-dev#53210)

* update docstring

* make a list of items

* update example

* update wording in docstring for more specific to groupby unique

* update grouped from GroupedBy

* correct output

Author: maikia

pandas/core/groupby/generic.py

@@ -1245,8 +1245,46 @@ def hist(
     def dtype(self) -> Series:
         return self.apply(lambda ser: ser.dtype)
 
-    @doc(Series.unique.__doc__)
     def unique(self) -> Series:
+        """
+        Return unique values for each group.
+
+        It returns unique values for each of the grouped values. Returned in
+        order of appearance. Hash table-based unique, therefore does NOT sort.
+
+        Returns
+        -------
+        Series
+            Unique values for each of the grouped values.
+
+        See Also
+        --------
+        Series.unique : Return unique values of Series object.
+
+        Examples
+        --------
+        >>> df = pd.DataFrame([('Chihuahua', 'dog', 6.1),
+        ...                    ('Beagle', 'dog', 15.2),
+        ...                    ('Chihuahua', 'dog', 6.9),
+        ...                    ('Persian', 'cat', 9.2),
+        ...                    ('Chihuahua', 'dog', 7),
+        ...                    ('Persian', 'cat', 8.8)],
+        ...                   columns=['breed', 'animal', 'height_in'])
+        >>> df
+               breed     animal   height_in
+        0  Chihuahua        dog         6.1
+        1     Beagle        dog        15.2
+        2  Chihuahua        dog         6.9
+        3    Persian        cat         9.2
+        4  Chihuahua        dog         7.0
+        5    Persian        cat         8.8
+        >>> ser = df.groupby('animal')['breed'].unique()
+        >>> ser
+        animal
+        cat              [Persian]
+        dog    [Chihuahua, Beagle]
+        Name: breed, dtype: object
+        """
         result = self._op_via_apply("unique")
         return result