docs: def readNullModelFile(nfile):
      """"
      reading file with null model info
  
      nfile   File containing null model info
      """
  
      params0_file = nfile+'.p0'
      nll0_file = nfile+'.nll0'
      assert os.path.exists(params0_file), '%s is missing.'%params0_file
      assert os.path.exists(nll0_file), '%s is missing.'%nll0_file
      params = SP.loadtxt(params0_file)
      NLL0 = SP.array([float(SP.loadtxt(nll0_file))])
  
  
      if params.ndim==1:
          rv = {'params0_g':SP.array([params[0]]),'params0_n':SP.array([params[1]]),'NLL0':NLL0}
      else:
          rv = {'params0_g':params[0],'params0_n':params[1],'NLL0':NLL0}
  
      return rv