Creating a template for jeremymanning's solution to problem 590

problems/590/jeremymanning.md

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+# [Problem 590: N-ary Tree Postorder Traversal](https://leetcode.com/problems/n-ary-tree-postorder-traversal/description/?envType=daily-question)
+
+## Initial thoughts (stream-of-consciousness)
+
+## Refining the problem, round 2 thoughts
+
+## Attempted solution(s)
+```python
+class Solution:  # paste your code here!
+    ...
+```