Return a copy of merkle tree after applying the txns
        :param txns:
        :return:

def treeWithAppliedTxns(self, txns: List, currentTree=None):
        """
        Return a copy of merkle tree after applying the txns
        :param txns:
        :return:
        """
        currentTree = currentTree or self.tree
        # Copying the tree is not a problem since its a Compact Merkle Tree
        # so the size of the tree would be 32*(lg n) bytes where n is the
        # number of leaves (no. of txns)
        tempTree = copy(currentTree)
        for txn in txns:
            s = self.serialize_for_tree(txn)
            tempTree.append(s)
        return tempTree