docs: def blur(dset,fwhm,prefix=None):
      '''blurs ``dset`` with given ``fwhm`` runs 3dmerge to blur dataset to given ``fwhm``
      default ``prefix`` is to suffix ``dset`` with ``_blur%.1fmm``'''
      if prefix==None:
          prefix = nl.suffix(dset,'_blur%.1fmm'%fwhm)
      return available_method('blur')(dset,fwhm,prefix)