code: def circuit_to_formula(circuit):
      # Convert the circuit to an equivalent formula.
      formula = nx.dag_to_branching(circuit)
      # Transfer the operator or variable labels for each node from the
      # circuit to the formula.
      for v in formula:
          source = formula.nodes[v]["source"]
          formula.nodes[v]["label"] = circuit.nodes[source]["label"]
      return formula
  
imports: import matplotlib.pyplot
  import networkx
label_desc: Use image node_id 1 for calling a global function with example usage: circuit_to_formula(circuit) and returns: formula