K Sum Paths

# Following is the Binary Tree node structure.
class BinaryTreeNode:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

from collections import deque
def kPathSum(root, k):
    ans=[]
    q=[]
    def dfs(x):
        if not x: return
        q.append(x.data)
        dfs(x.left)
        dfs(x.right)
        val=0
        for i in range(len(q)-1,-1,-1):
            val+=q[i]
            if val==k:ans.append(q[i:][:])
        q.pop()
    dfs(root)
    return ans