def METHOD_NAME():
    """Set up the look-up tables for levels as a function of input byte.
    For 1-bit mode, one has just the sign bit:
     === =====
      s  value
     === =====
      0  +1
      1  -1
     === =====
    For 2-bit mode, there is a sign and a magnitude, which encode:
     === === ===== =====
      m   s  value s*2+m
     === === ===== =====
      0   0  -Hi    0
      0   1  +1     2
      1   0  -1     1
      1   1  +Hi    3
     === === ===== =====
    Note that the sign bit is flipped for 1-bit mode from what one might
    expect from the 2-bit encodings (at least, as implemented in mark5access;
    the docs are rather unclear).  For more details, see Table 13 in
    https://library.nrao.edu/public/memos/vlba/up/VLBASU_13.pdf
    and
    https://www.haystack.mit.edu/tech/vlbi/mark5/docs/Mark%205B%20users%20manual.pdf
    Appendix A: sign always on even bit stream (0, 2, 4, ...), and magnitude
    on adjacent odd stream (1, 3, 5, ...).
    In the above table, the last column is the index in the linearly increasing
    table of levels (``decoder_levels[2]``).
    """
    b = np.arange(256)[:, np.newaxis]
    sl = np.arange(8)
    # For 1-bit modes, like for Mark 4, if set, sign=-1, so need to get item 0.
    # With this, one reproduces mark5access m5d, but must say that from the
    # documentation, it is not obvious this is correct.
    lut1bit = decoder_levels[1][((b >> sl) & 1) ^ 1]
    # 2-bit mode: sign bit in lower position thatn magnitude bit
    # ms=00,01,10,11 = -Hi, 1, -1, Hi (lut
    s = np.arange(0, 8, 2)  # 0, 2, 4, 6
    m = s + 1               # 1, 3, 5, 7
    sl = (((b >> s) & 1) << 1) + ((b >> m) & 1)
    lut2bit = decoder_levels[2][sl]
    return lut1bit, lut2bit