DataFrame products
+-------------+--------+
| Column Name | Type   |
+-------------+--------+
| name        | object |
| quantity    | int    |
| price       | int    |
+-------------+--------+

Write a solution to fill in the missing value as 0 in the quantity column.

The result format is in the following example.

Example 1:
Input:+-----------------+----------+-------+
| name            | quantity | price |
+-----------------+----------+-------+
| Wristwatch      | 32       | 135   |
| WirelessEarbuds | None     | 821   |
| GolfClubs       | None     | 9319  |
| Printer         | 849      | 3051  |
+-----------------+----------+-------+
Output:
+-----------------+----------+-------+
| name            | quantity | price |
+-----------------+----------+-------+
| Wristwatch      | 32       | 135   |
| WirelessEarbuds | 0        | 821   |
| GolfClubs       | 0        | 9319  |
| Printer         | 849      | 3051  |
+-----------------+----------+-------+
Explanation: 
The quantity for Toaster and Headphones are filled by 0.