@classmethod
def from_specline(cls, aline, z, zlim):
    """ From AbsLine or Emline

        Parameters
        ----------
        aline : AbsLine
        z : float
          Redshift
        zlim : tuple of floats
          Redshift limits for a line
        """
    from ..spectralline import AbsLine, EmLine
    if not isinstance(aline, (AbsLine, EmLine)):
        raise IOError('Input aline must be AbsLine or EmLine')
    slf = cls(z, zlim, wrest=aline.wrest)
    return slf
