code: def _populate_sgc_payoff_arrays(payoff_arrays):
      
      n = payoff_arrays[0].shape[0]  # 4*k-1
      m = (n+1)//2 - 1  # 2*k-1
      for payoff_array in payoff_arrays:
          for i in range(m):
              for j in range(m):
                  payoff_array[i, j] = 0.75
              for j in range(m, n):
                  payoff_array[i, j] = 0.5
          for i in range(m, n):
              for j in range(n):
                  payoff_array[i, j] = 0
  
          payoff_array[0, m-1] = 1
          payoff_array[0, 1] = 0.5
          for i in range(1, m-1):
              payoff_array[i, i-1] = 1
              payoff_array[i, i+1] = 0.5
          payoff_array[m-1, m-2] = 1
          payoff_array[m-1, 0] = 0.5
  
      k = (m+1)//2
      for h in range(k):
          i, j = m + 2*h, m + 2*h
          payoff_arrays[0][i, j] = 0.75
          payoff_arrays[0][i+1, j+1] = 0.75
          payoff_arrays[1][j, i+1] = 0.75
          payoff_arrays[1][j+1, i] = 0.75
docs: Populate the ndarrays in `payoff_arrays` with the payoff values of
      the SGC game.
  
      Parameters
      ----------
      payoff_arrays : tuple(ndarray(float, ndim=2))
          Tuple of 2 ndarrays of shape (4*k-1, 4*k-1). Modified in place.