Examples
    ========

    >>> from sympy.physics.quantum import represent, Dagger
    >>> from sympy.physics.quantum.pauli import SigmaMinus
    >>> sm = SigmaMinus()
    >>> sm
    SigmaMinus()
    >>> Dagger(sm)
    SigmaPlus()
    >>> represent(sm)
    Matrix([
    [0, 0],
    [1, 0]])
    c