code: def NumRegressors(npix, pld_order, cross_terms=True):
      '''
      Return the number of regressors for `npix` pixels
      and PLD order `pld_order`.
  
      :param bool cross_terms: Include pixel cross-terms? Default :py:obj:`True`
  
      '''
  
      res = 0
      for k in range(1, pld_order + 1):
          if cross_terms:
              res += comb(npix + k - 1, k)
          else:
              res += npix
      return int(resf NumRegressors(npix, pld_order, cross_terms=True):
      '''
      Return the number of regressors for `npix` pixels
      and PLD order `pld_order`.
  
      :param bool cross_terms: Include pixel cross-terms? Default :py:obj:`True`
  
      '''
  
      res = 0
      for k in range(1, pld_order + 1):
          if cross_terms:
              res += comb(npix + k - 1, k)
          else:
              res += npix
      return int(res)
docs: Return the number of regressors for `npix` pixels
      and PLD order `pld_order`.
  
      :param bool cross_terms: Include pixel cross-terms? Default :py:obj:`True`