docs: def scalarmult_B(e):
      """
      Implements scalarmult(B, e) more efficiently.
      """
      # scalarmult(B, l) is the identity
      e %= L
      P = IDENT
      for i in range(253):
          if e & 1:
              P = edwards_add(P=P, Q=Bpow[i])
          e //= 2
      assert e == 0, e
      return P