[BUG] Cannot cleanup sample Circuit

[Seva-Vaskin]

To Reproduce

1. Write simple code

from cirbo.core import Circuit, Gate
from cirbo.minimization import cleanup

circ = Circuit.from_bench_file("data/circuit.bench")
circ = cleanup(circ)

2. See stacktrace:

---------------------------------------------------------------------------
CircuitValidationError                    Traceback (most recent call last)
Cell In[10], line 1
----> 1 circ = cleanup(circ)
      2 # circ.into_graphviz_digraph()

File ~/Work/cirbo/cirbo/minimization/simplification/cleanup.py:28, in cleanup(circuit)
     19 def cleanup(circuit: Circuit) -> Circuit:
     20     """
     21     Applies several simplification algorithms from this module consecutively in order to
     22     simplify provided circuit.
   (...)
     26 
     27     """
---> 28     return Transformer.apply_transformers(
     29         circuit,
     30         [
     31             RemoveRedundantGates(),
     32             MergeUnaryOperators(),
     33             MergeDuplicateGates(),
     34             MergeEquivalentGates(),
     35         ],
     36     )

File ~/Work/cirbo/cirbo/core/circuit/transformer.py:100, in Transformer.apply_transformers(circuit, transformers)
     97     _transformers = transformers
     99 # apply transformers to the circuit.
--> 100 return functools.reduce(
    101     lambda _circ, _transformer: _transformer._transform(_circ),
    102     Transformer.linearize_reduce_transformers(_transformers),
    103     circuit,
    104 )

File ~/Work/cirbo/cirbo/core/circuit/transformer.py:101, in Transformer.apply_transformers.<locals>.<lambda>(_circ, _transformer)
     97     _transformers = transformers
     99 # apply transformers to the circuit.
    100 return functools.reduce(
--> 101     lambda _circ, _transformer: _transformer._transform(_circ),
    102     Transformer.linearize_reduce_transformers(_transformers),
    103     circuit,
    104 )

File ~/Work/cirbo/cirbo/minimization/simplification/merge_equivalent_gates.py:43, in MergeEquivalentGates._transform(self, circuit)
     37 """
     38 :param circuit: the original circuit to be simplified
     39 :return: new simplified version of the circuit
     40 
     41 """
     42 equivalent_gate_groups = _find_equivalent_gates_groups(circuit)
---> 43 return _replace_equivalent_gates(circuit, equivalent_gate_groups)

File ~/Work/cirbo/cirbo/minimization/simplification/merge_equivalent_gates.py:119, in _replace_equivalent_gates(circuit, equivalent_groups)
    116     return
    118 # reconstruct circuit
--> 119 more_itertools.consume(
    120     circuit.dfs(
    121         circuit.outputs,
    122         on_exit_hook=_process_gate,
    123         unvisited_hook=_process_gate,
    124         topsort_unvisited=True,
    125     )
    126 )
    128 # reorder inputs according to original order
    129 _new_circuit.set_inputs(circuit.inputs)

File ~/.cache/pypoetry/virtualenvs/cirbo-Ev1XhC9r-py3.10/lib/python3.10/site-packages/more_itertools/recipes.py:184, in consume(iterator, n)
    181 # Use functions that consume iterators at C speed.
    182 if n is None:
    183     # feed the entire iterator into a zero-length deque
--> 184     deque(iterator, maxlen=0)
    185 else:
    186     # advance to the empty slice starting at position n
    187     next(islice(iterator, n, n), None)

File ~/Work/cirbo/cirbo/core/circuit/circuit.py:2179, in Circuit._traverse_circuit(self, mode, start_gates, inverse, on_enter_hook, on_discover_hook, on_exit_hook, unvisited_hook, on_traversal_end_hook, topsort_unvisited)
   2176     yield current_elem
   2178 elif gate_states[current_elem.label] == TraverseState.ENTERED:
-> 2179     on_exit_hook(current_elem, gate_states)
   2180     gate_states[current_elem.label] = TraverseState.VISITED
   2181     queue.pop(pop_index)

File ~/Work/cirbo/cirbo/minimization/simplification/merge_equivalent_gates.py:111, in _replace_equivalent_gates.<locals>._process_gate(_gate, _)
    107 nonlocal _new_circuit, _old_to_new_gate
    109 # Add all gates, even equivalent ones, but link
    110 # users of the latest to "keep" representative.
--> 111 _new_circuit.emplace_gate(
    112     label=_gate.label,
    113     gate_type=_gate.gate_type,
    114     operands=tuple(map(_get_gate_new_name, _gate.operands)),
    115 )
    116 return

File ~/Work/cirbo/cirbo/core/circuit/circuit.py:456, in Circuit.emplace_gate(self, label, gate_type, operands, **kwargs)
    445 """
    446 Add gate in the circuit.
    447 
   (...)
    453 
    454 """
    455 check_label_doesnt_exist(label, self)
--> 456 check_gates_exist(operands, self)
    458 return self._emplace_gate(label, gate_type, operands, **kwargs)

File ~/Work/cirbo/cirbo/core/circuit/validation.py:32, in check_gates_exist(gates, circuit)
     30 for gate_label in gates:
     31     if not circuit.has_gate(gate_label):
---> 32         raise CircuitValidationError(
     33             f'Gate {gate_label} are not initialized in the circuit',
     34         )

CircuitValidationError: Gate z2 are not initialized in the circuit

Expected behavior
Circuit is cleaned up

Desktop:

• OS: Ubuntu
• Version 22.04.5 LTS