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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _transform_delta(f:Formula, formula2AtomicFormula):
 """From a Propositional Formula to a Propositional Formula with non-propositional subformulas replaced with a "freezed" atomic formula."""

    t = type(f)
    if t == PLNot:
        return PLNot(_transform_delta(f, formula2AtomicFormula))
    # elif isinstance(f, PLBinaryOperator): #PLAnd, PLOr, PLImplies, PLEquivalence
    elif t == PLAnd or t == PLOr or t == PLImplies or t == PLEquivalence:
        return t([_transform_delta(subf, formula2AtomicFormula) for subf in f.formulas])
    elif t == PLTrue or t == PLFalse:
        return f
    else:
        return formula2AtomicFormula[f]