how to reduce dataFrame wisely

Question

I want to transform the following dataFrmae structure where we have details regarding each id and kpi couple of records one with the value_left and the 2nd for the value_right I want to group the 2 records into a single record (as you see in the expected results)

i want to reduce the fillowing dataFrame

+---+---+----------+-----------+
| id|kpi|value_left|value_right|
+---+---+----------+-----------+
|  1|sum|        10|       null|
|  1|sum|      null|         20|
|  2|avg|        15|       null|
|  2|avg|      null|         15|
+---+---+----------+-----------+

Expected output dataFrame

+---+---+----------+-----------+
| id|kpi|value_left|value_right|
+---+---+----------+-----------+
|  1|sum|        10|         20|
|  2|avg|        15|         15|
+---+---+----------+-----------+

expected dataFrame