def has_block(index):
    return os.path.isfile(os.path.join(self.nodes[node_number].datadir, self.chain, 'blocks', f'blk{index:05}.dat'))
def has_block(index):
    return os.path.isfile(os.path.join(self.nodes[node_number].datadir, self.chain, 'blocks', f'blk{index:05}.dat'))