<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_fixed_params(im):
 """ Parameters that the user has no influence on. Mostly chosen bases on the input images. """

    
    p = Parameters()
    
    if not isinstance(im, np.ndarray):
        return p
    
    # Dimension of the inputs
    p.FixedImageDimension = im.ndim
    p.MovingImageDimension = im.ndim
    
    # Always write result, so I can verify
    p.WriteResultImage = True
    
    # How to write the result
    tmp = DTYPE_NP2ITK[im.dtype.name]
    p.ResultImagePixelType = tmp.split('_')[-1].lower()
    p.ResultImageFormat = "mhd"
    
    # Done
    return p