human
Solve the following python programming problem given the following code:
def find_source_table(expr) : 
    node = expr.op () 
    first_tables = [] 
    def push_first(arg) : 
        if (not isinstance (arg, ir.Expr)) : 
            return 
if isinstance (arg, ir.TableExpr) : 
            first_tables.append (arg) 
else : 
            collect (arg.op ()) 
def collect(node) : 
        for arg in node.flat_args () : 
            push_first (arg) 
collect (node) 
    options = util.unique_by_key (options, id) 
    if (len (options) > 1) : 
        raise NotImplementedError 
return options [0] 

    
    

    Fix the buggy line: options = util.unique_by_key (options, id)
assistant
#Here is Python program to fix the buggy line: options = util.

options = util.unique_by_key (first_tables, id)