DOC: add example to insert (pandas-dev#39313)

Author: nofarmish

pandas/core/frame.py

@@ -3870,6 +3870,13 @@ def insert(self, loc, column, value, allow_duplicates: bool = False) -> None:
            col1  col1  newcol  col2
         0   100     1      99     3
         1   100     2      99     4
+
+        Notice that Pandas uses index alignment in case of `value` from type `Series`:
+        >>> df.insert(0, "col0", pd.Series([5, 6], index=[1, 2]))
+        >>> df
+           col0  col1  col1  newcol  col2
+        0   NaN   100     1      99     3
+        1   5.0   100     2      99     4
         """
         if allow_duplicates and not self.flags.allows_duplicate_labels:
             raise ValueError(