<pre> DataFrame <code>products</code> +-------------+--------+ | Column Name | Type | +-------------+--------+ | name | object | | quantity | int | | price | int | +-------------+--------+ </pre> <p>Write a solution to fill in the missing value as <code><strong>0</strong></code> in the <code>quantity</code> column.</p> <p>The result format is in the following example.</p> <p> </p> <pre> <strong class="example">Example 1:</strong> <strong>Input:</strong>+-----------------+----------+-------+ | name | quantity | price | +-----------------+----------+-------+ | Wristwatch | None | 135 | | WirelessEarbuds | None | 821 | | GolfClubs | 779 | 9319 | | Printer | 849 | 3051 | +-----------------+----------+-------+ <strong>Output: </strong>+-----------------+----------+-------+ | name | quantity | price | +-----------------+----------+-------+ | Wristwatch | 0 | 135 | | WirelessEarbuds | 0 | 821 | | GolfClubs | 779 | 9319 | | Printer | 849 | 3051 | +-----------------+----------+-------+ <strong>Explanation:</strong> The quantity for Wristwatch and WirelessEarbuds are filled by 0.</pre>