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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 refocus(field, d, nm, res, method="helmholtz", num_cpus=1, padding=True):
 """Refocus a 1D or 2D field Parameters field : 1d or 2d array 1D or 2D background corrected electric field (Ex/BEx) d : float Distance to be propagated in pixels (negative for backwards) nm : float Refractive index of medium res : float Wavelenth in pixels method : str Defines the method of propagation; one of - "helmholtz" : the optical transfer function `exp(idkₘ(M-1))` - "fresnel" : paraxial approximation `exp(idk²/kₘ)` num_cpus : int Not implemented. Only one CPU is used. padding : bool perform padding with linear ramp from edge to average to reduce ringing artifacts. .. versionadded:: 0.1.4 Returns ------- Electric field at `d`. """

    # FFT of field
    fshape = len(field.shape)
    assert fshape in [1, 2], "Dimension of `field` must be 1 or 2."

    func = fft_propagate
    names = func.__code__.co_varnames[:func.__code__.co_argcount]

    loc = locals()
    vardict = dict()

    for name in names:
        if name in loc:
            vardict[name] = loc[name]

    if padding:
        field = pad.pad_add(field)

    vardict["fftfield"] = np.fft.fftn(field)

    refoc = func(**vardict)

    if padding:
        refoc = pad.pad_rem(refoc)

    return refoc