human
Solve the following python programming problem given the following code:
@ storage_format_upgrade ('Convert inode blocks list to treetree', upgrade_from = { 
    'inode_format' : None, 
}, upgrade_to = { 
    'inode_format' : 'treetree', 
}) 
def convert_fs_to_treetree_inodes(eg) : 
    '
    Convert an existing filesystem from the "inode with flat list of blocks"
    format to the "inode with treetree of blocks" format.
    ' 
    inode_index = eg.root ['inodes'] 
    class DummyStorage (object) : 
        def _autocommit(self) : 
            pass 
s = DummyStorage () 
    for inode_name in inode_index : 
        upgrade_log.debug ('Reorganizing inode %r', inode_name) 
        inode = StorageInode (inode_name, inode_index [inode_name], s) 
        block_offsets = set () 
        for old_block_name in inode.tree : 
            if old_block_name.startswith ('b') : 
                if (not old_block_name.startswith ('bt')) : 
                    block_offsets.add (int (old_block_name [1 :])) 
for block_offset in sorted (block_offsets) : 
            old_block_name = ('b%d' % block_offset) 
            new_block_name = str ((block_offset / StorageInode.blocksize)) 
            old_block = inode.tree [old_block_name] 
            new_block = inode.tt.clone (old_block, new_block_name) 
            del inode.tree [eg] 
inode ['size'] = (block_offset + len (new_block.data)) 
        inode.tree._commit () 

    
    

    Fix the buggy line: del inode.tree [eg]
assistant
#Here is Python code to fix the buggy line: del inode.

del inode.tree [old_block_name]