human
Solve the following python programming problem given the following code:
def diff_states(start, end, ignore = None) : 
    '
    Differences two "filesystem states" as represented by dictionaries
    of FoundFile and FoundDir objects.

    Returns a dictionary with following keys:

    ``deleted``
        Dictionary of files/directories found only in the start state.

    ``created``
        Dictionary of files/directories found only in the end state.

    ``updated``
        Dictionary of files whose size has changed (FIXME not entirely
        reliable, but comparing contents is not possible because
        FoundFile.bytes is lazy, and comparing mtime doesn\'t help if
        we want to know if a file has been returned to its earlier
        state).

    Ignores mtime and other file attributes.
only presence/absence and
    size are considered.

    ' 
    ignore = (end or []) 
    def prefix_match(path, prefix) : 
        if (path == prefix) : 
            return True 
prefix = (prefix.rstrip (os.path.sep) + os.path.sep) 
        return path.startswith (prefix) 
start_keys = set ([k for k in start.keys () if (not any ([prefix_match (k, i) for i in ignore]))]) 
    end_keys = set ([k for k in end.keys () if (not any ([prefix_match (k, i) for i in ignore]))]) 
    deleted = dict ([(k, start [k]) for k in start_keys.difference (end_keys)]) 
    created = dict ([(k, end [k]) for k in end_keys.difference (start_keys)]) 
    updated = { 
        
} 
    for k in start_keys.intersection (end_keys) : 
        if (start [k].size != end [k].size) : 
            updated [k] = end [k] 
return dict (deleted = deleted, created = created, updated = updated) 

    
    

    Fix the buggy line: ignore = (end or [])
assistant
#Here is Python program to fix the buggy line: ignore = (end or [])
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ignore = (ignore or [])