code: def publickey_unsafe(sk):
      
      h = H(sk)
      a = 2 ** (b - 2) + sum(2 ** i * bit(h, i) for i in range(3, b - 2))
      A = scalarmult_B(a)
      return encodepoint(A)
docs: Not safe to use with secret keys or secret data.
  
      See module docstring.  This function should be used for testing only.