Added an example for infer_freq

Added an example for infer_freq function. The initial index is built using a fixed number of periods to avoid encoding frequency in this index explicitly.

Author: Remit

pandas/tseries/frequencies.py

@@ -139,6 +139,13 @@ def infer_freq(index, warn: bool = True) -> Optional[str]:
         If the index is not datetime-like.
     ValueError
         If there are fewer than three values.
+        
+    Examples
+    --------
+    >>> idx = pd.date_range(start = '2020/12/01', end = '2020/12/30', periods = 30)
+    >>> pd.infer_freq(idx)
+    'D'
+            
     """
     import pandas as pd