code: def from_file(cls, filename, **kwargs):
          
          if 'flux_unit' not in kwargs:
              kwargs['flux_unit'] = cls._internal_flux_unit
  
          if ((filename.endswith('fits') or filename.endswith('fit')) and
                  'flux_col' not in kwargs):
              kwargs['flux_col'] = 'THROUGHPUT'
  
          header, wavelengths, throughput = specio.read_spec(filename, **kwargs)
          return cls(Empirical1D, points=wavelengths, lookup_table=throughput,
                     keep_neg=True, meta={'header': header})
docs: Creates a bandpass from file.
  
          If filename has 'fits' or 'fit' suffix, it is read as FITS.
          Otherwise, it is read as ASCII.
  
          Parameters
          ----------
          filename : str
              Bandpass filename.
  
          kwargs : dict
              Keywords acceptable by
              :func:`~synphot.specio.read_fits_spec` (if FITS) or
              :func:`~synphot.specio.read_ascii_spec` (if ASCII).
  
          Returns
          -------
          bp : `SpectralElement`
              Empirical bandpass.