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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def Trim(self, flags):
 """ Trim the nodes from the tree keeping only the root hash. Args: flags: "0000" for trimming, any other value for keeping the nodes. """

        logger.info("Trimming!")
        flags = bytearray(flags)
        length = 1 << self.Depth - 1
        while len(flags) < length:
            flags.append(0)

        MerkleTree._TrimNode(self.Root, 0, self.Depth, flags)