def delete_backward_blank(node):
    while True:
        node = node.next
        if (node and (node.type == NodeType.BLANK)):
            node = delete_node(node)
            node = node.last
        else:
            return
def delete_backward_blank(node):
    while True:
        node = node.next
        if (node and (node.type == NodeType.BLANK)):
            node = delete_node(node)
            node = node.last
        else:
            return