Maximum Depth of Binary Tree

class Solution:
	def maxDepth(self, root: Optional[TreeNode]) -> int:
		def get_depth(node):
			if not node:
				return 0
			cmax = 0
			cmax = max(cmax, 1 + get_depth(node.left))
			cmax = max(cmax, 1 + get_depth(node.right))
			return cmax
		return get_depth(root)