def rep_innerproduct(expr, **options):
    """
    Returns an innerproduct like representation (e.g. ``<x'|x>``) for the
    given state.

    Attempts to calculate inner product with a bra from the specified
    basis. Should only be passed an instance of KetBase or BraBase

    Parameters
    ==========

    expr : KetBase or BraBase
        The expression to be represented

    Examples
    ========

    >>> from sympy.physics.quantum.represent import rep_innerproduct
    >>> from sympy.physics.quantum.cartesian import XOp, XKet, PxOp, PxKet
    >>> rep_innerproduct(XKet())
    DiracDelta(x - x_1)
    >>> rep_innerproduct(XKet(), basis=PxOp())
    sqrt(2)*exp(-I*px_1*x/hbar)/(2*sqrt(hbar)*sqrt(pi))
    >>> rep_innerproduct(PxKet(), basis=XOp())
    sqrt(2)*exp(I*px*x_1/hbar)/(2*sqrt(hbar)*sqrt(pi))

    """

    if not isinstance(expr, (KetBase, BraBase)):
        raise TypeError("expr passed is not a Bra or Ket")

    basis = get_basis(expr, **options)

    if not isinstance(basis, StateBase):
        raise NotImplementedError("Can't form this representation!")

    if not options in "index":
        options["index"] = 1

    basis_kets = enumerate_states(basis, options["index"], 2)

    if isinstance(expr, BraBase):
        bra = expr
        ket = (basis_kets[1] if basis_kets[0].dual == expr else basis_kets[0])
    else:
        bra = (basis_kets[1].dual if basis_kets[0]
               == expr else basis_kets[0].dual)
        ket = expr

    prod = InnerProduct(bra, ket)
    result = prod.doit()

    format = options.get('format', 'sympy')
    return expr._format_represent(result, format)
dataset/ETHPy150Open sympy/sympy/sympy/physics/quantum/represent.py/rep_innerproduct/swapped operands of `in`