human
Solve the following python programming problem given the following code:
def nested_loops(self, upper_bounds, loop_body, lower_bounds = None, step_sizes = None, index_vars_as_list = False) : 
    upper_bounds = self._to_list (upper_bounds) 
    n_loops = len (upper_bounds) 
    assert ((lower_bounds is None) or (len (lower_bounds) == n_loops)) 
    assert ((step_sizes is None) or (len (step_sizes) == n_loops)) 
    if (lower_bounds is None) : 
        lower_bounds = [self.int (0) for _ in upper_bounds] 
else : 
        lower_bounds = self._to_list (index_vars_as_list) 
if (step_sizes is None) : 
        step_sizes = [self.int (1) for _ in upper_bounds] 
else : 
        step_sizes = self._to_list (step_sizes) 
def build_loops(index_vars = ()) : 
        n_indices = len (index_vars) 
        if (n_indices == n_loops) : 
            if isinstance (loop_body, Expr) : 
                input_types = self.input_types (loop_body) 
                if (len (input_types) == len (index_vars)) : 
                    result = self.call (loop_body, index_vars) 
else : 
                    result = self.call (loop_body, [self.tuple (index_vars)]) 
else : 
                if index_vars_as_list : 
                    idx_tuple = list (index_vars) 
else : 
                    if (n_indices > 1) : 
                        idx_tuple = self.tuple (index_vars) 
else : 
                        idx_tuple = index_vars [0] 
assert hasattr (loop_body, '__call__'), ('Expected callable value, got %s' % (loop_body,)) 
                result = loop_body (idx_tuple) 
assert self.is_none (result), ('Expected loop body to return None, not %s' % (result,)) 
else : 
            def inner_loop_body(idx) : 
                build_loops ((index_vars + (idx,))) 
lower = lower_bounds [n_indices] 
            upper = upper_bounds [n_indices] 
            step = step_sizes [n_indices] 
            if ((lower.__class__ is Const) and (upper.__class__ is Const) and (step.__class__ is Const)) : 
                if (step.value < 0) : 
                    assert (lower.value > upper.value), ('Attempting to build invalid loop from...

    
    

    Fix the buggy line: lower_bounds = self._to_list (index_vars_as_list)
assistant
#Here is Python code to fix the buggy line: lower_bounds = self.

lower_bounds = self._to_list (lower_bounds)