code: def filter_by_missing(max_miss=0.01):
      
  
      def f(G, bim):
          Isnp = sp.isnan(G).mean(0) < max_miss
          G_out = G[:, Isnp]
          bim_out = bim[Isnp]
          return G_out, bim_out
  
      return f
docs: return function that filters by missing values
      (takes maximum fraction of missing values, default is 0.01)