DOC: fix ES01 for pandas.core.resample.Resampler.indices (#60835)

Author: tuhinsharma121

pandas/core/groupby/groupby.py

@@ -570,6 +570,13 @@ def indices(self) -> dict[Hashable, npt.NDArray[np.intp]]:
         """
         Dict {group name -> group indices}.
 
+        The dictionary keys represent the group labels (e.g., timestamps for a
+        time-based resampling operation), and the values are arrays of integer
+        positions indicating where the elements of each group are located in the
+        original data. This property is particularly useful when working with
+        resampled data, as it provides insight into how the original time-series data
+        has been grouped.
+
         See Also
         --------
         core.groupby.DataFrameGroupBy.indices : Provides a mapping of group rows to