(cls, arg)
Evaluates the Dagger instance.

        Examples
        ========

        >>> from sympy import I
        >>> from sympy.physics.secondquant import Dagger, B, Bd
        >>> Dagger(2*I)
        -2*I
        >>> Dagger(B(0))
        CreateBoson(0)
        >>> Dagger(Bd(0))
        AnnihilateBoson(0)

        The eval() method is called automatically.
Evaluates the Dagger instance.
Evaluates the Dagger instance .
def eval(cls, arg):
        """
        Evaluates the Dagger instance.

        Examples
        ========

        >>> from sympy import I
        >>> from sympy.physics.secondquant import Dagger, B, Bd
        >>> Dagger(2*I)
        -2*I
        >>> Dagger(B(0))
        CreateBoson(0)
        >>> Dagger(Bd(0))
        AnnihilateBoson(0)

        The eval() method is called automatically.

        """
        try:
            d = arg._dagger_()
        except AttributeError:
            if isinstance(arg, Basic):
                if arg.is_Add:
                    return Add(*tuple(map(Dagger, arg.args)))
                if arg.is_Mul:
                    return Mul(*tuple(map(Dagger, reversed(arg.args))))
                if arg.is_Number:
                    return arg
                if arg.is_Pow:
                    return Pow(Dagger(arg.args[0]), arg.args[1])
                if arg == I:
                    return -arg
            else:
                return None
        else:
            return d
def eval ( cls , arg ) : try : d = arg . _dagger_ ( ) except AttributeError : if isinstance ( arg , Basic ) : if arg . is_Add : return Add ( * tuple ( map ( Dagger , arg . args ) ) ) if arg . is_Mul : return Mul ( * tuple ( map ( Dagger , reversed ( arg . args ) ) ) ) if arg . is_Number : return arg if arg . is_Pow : return Pow ( Dagger ( arg . args [ 0 ] ) , arg . args [ 1 ] ) if arg == I : return - arg else : return None else : return d