docs: def _transform(self, inp):
          """Basic MD5 step transforming the digest based on the input.
  
          Note that if the Mysterious Constants are arranged backwards
          in little-endian order and decrypted with the DES they produce
          OCCULT MESSAGES!
          """
  
          a, b, c, d = A, B, C, D = self.A, self.B, self.C, self.D
  
          # Round 1.
  
          S11, S12, S13, S14 = 7, 12, 17, 22
  
          a = XX(F, a, b, c, d, inp[ 0], S11, 0xD76AA478L) # 1 
          d = XX(F, d, a, b, c, inp[ 1], S12, 0xE8C7B756L) # 2 
          c = XX(F, c, d, a, b, inp[ 2], S13, 0x242070DBL) # 3 
          b = XX(F, b, c, d, a, inp[ 3], S14, 0xC1BDCEEEL) # 4 
          a = XX(F, a, b, c, d, inp[ 4], S11, 0xF57C0FAFL) # 5 
          d = XX(F, d, a, b, c, inp[ 5], S12, 0x4787C62AL) # 6 
          c = XX(F, c, d, a, b, inp[ 6], S13, 0xA8304613L) # 7 
          b = XX(F, b, c, d, a, inp[ 7], S14, 0xFD469501L) # 8 
          a = XX(F, a, b, c, d, inp[ 8], S11, 0x698098D8L) # 9 
          d = XX(F, d, a, b, c, inp[ 9], S12, 0x8B44F7AFL) # 10 
          c = XX(F, c, d, a, b, inp[10], S13, 0xFFFF5BB1L) # 11 
          b = XX(F, b, c, d, a, inp[11], S14, 0x895CD7BEL) # 12 
          a = XX(F, a, b, c, d, inp[12], S11, 0x6B901122L) # 13 
          d = XX(F, d, a, b, c, inp[13], S12, 0xFD987193L) # 14 
          c = XX(F, c, d, a, b, inp[14], S13, 0xA679438EL) # 15 
          b = XX(F, b, c, d, a, inp[15], S14, 0x49B40821L) # 16 
  
          # Round 2.
  
          S21, S22, S23, S24 = 5, 9, 14, 20
  
          a = XX(G, a, b, c, d, inp[ 1], S21, 0xF61E2562L) # 17 
          d = XX(G, d, a, b, c, inp[ 6], S22, 0xC040B340L) # 18 
          c = XX(G, c, d, a, b, inp[11], S23, 0x265E5A51L) # 19 
          b = XX(G, b, c, d, a, inp[ 0], S24, 0xE9B6C7AAL) # 20 
          a = XX(G, a, b, c, d, inp[ 5], S21, 0xD62F105DL) # 21 
          d = XX(G, d, a, b, c, inp[10], S22, 0x02441453L) # 22 
          c = XX(G, c, d, a, b, inp[15], S23, 0xD8A1E681L) # 23 
          b = XX(G, b, c, d, a, inp[ 4], S24, 0xE7D3FBC8L) # 24 
          a = XX(G, a, b, c, d, inp[ 9], S21, 0x21E1CDE6L) # 25 
          d = XX(G, d, a, b, c, inp[14], S22, 0xC33707D6L) # 26 
          c = XX(G, c, d, a, b, inp[ 3], S23, 0xF4D50D87L) # 27 
          b = XX(G, b, c, d, a, inp[ 8], S24, 0x455A14EDL) # 28 
          a = XX(G, a, b, c, d, inp[13], S21, 0xA9E3E905L) # 29 
          d = XX(G, d, a, b, c, inp[ 2], S22, 0xFCEFA3F8L) # 30 
          c = XX(G, c, d, a, b, inp[ 7], S23, 0x676F02D9L) # 31 
          b = XX(G, b, c, d, a, inp[12], S24, 0x8D2A4C8AL) # 32 
  
          # Round 3.
  
          S31, S32, S33, S34 = 4, 11, 16, 23
  
          a = XX(H, a, b, c, d, inp[ 5], S31, 0xFFFA3942L) # 33 
          d = XX(H, d, a, b, c, inp[ 8], S32, 0x8771F681L) # 34 
          c = XX(H, c, d, a, b, inp[11], S33, 0x6D9D6122L) # 35 
          b = XX(H, b, c, d, a, inp[14], S34, 0xFDE5380CL) # 36 
          a = XX(H, a, b, c, d, inp[ 1], S31, 0xA4BEEA44L) # 37 
          d = XX(H, d, a, b, c, inp[ 4], S32, 0x4BDECFA9L) # 38 
          c = XX(H, c, d, a, b, inp[ 7], S33, 0xF6BB4B60L) # 39 
          b = XX(H, b, c, d, a, inp[10], S34, 0xBEBFBC70L) # 40 
          a = XX(H, a, b, c, d, inp[13], S31, 0x289B7EC6L) # 41 
          d = XX(H, d, a, b, c, inp[ 0], S32, 0xEAA127FAL) # 42 
          c = XX(H, c, d, a, b, inp[ 3], S33, 0xD4EF3085L) # 43 
          b = XX(H, b, c, d, a, inp[ 6], S34, 0x04881D05L) # 44 
          a = XX(H, a, b, c, d, inp[ 9], S31, 0xD9D4D039L) # 45 
          d = XX(H, d, a, b, c, inp[12], S32, 0xE6DB99E5L) # 46 
          c = XX(H, c, d, a, b, inp[15], S33, 0x1FA27CF8L) # 47 
          b = XX(H, b, c, d, a, inp[ 2], S34, 0xC4AC5665L) # 48 
  
          # Round 4.
  
          S41, S42, S43, S44 = 6, 10, 15, 21
  
          a = XX(I, a, b, c, d, inp[ 0], S41, 0xF4292244L) # 49 
          d = XX(I, d, a, b, c, inp[ 7], S42, 0x432AFF97L) # 50 
          c = XX(I, c, d, a, b, inp[14], S43, 0xAB9423A7L) # 51 
          b = XX(I, b, c, d, a, inp[ 5], S44, 0xFC93A039L) # 52 
          a = XX(I, a, b, c, d, inp[12], S41, 0x655B59C3L) # 53 
          d = XX(I, d, a, b, c, inp[ 3], S42, 0x8F0CCC92L) # 54 
          c = XX(I, c, d, a, b, inp[10], S43, 0xFFEFF47DL) # 55 
          b = XX(I, b, c, d, a, inp[ 1], S44, 0x85845DD1L) # 56 
          a = XX(I, a, b, c, d, inp[ 8], S41, 0x6FA87E4FL) # 57 
          d = XX(I, d, a, b, c, inp[15], S42, 0xFE2CE6E0L) # 58 
          c = XX(I, c, d, a, b, inp[ 6], S43, 0xA3014314L) # 59 
          b = XX(I, b, c, d, a, inp[13], S44, 0x4E0811A1L) # 60 
          a = XX(I, a, b, c, d, inp[ 4], S41, 0xF7537E82L) # 61 
          d = XX(I, d, a, b, c, inp[11], S42, 0xBD3AF235L) # 62 
          c = XX(I, c, d, a, b, inp[ 2], S43, 0x2AD7D2BBL) # 63 
          b = XX(I, b, c, d, a, inp[ 9], S44, 0xEB86D391L) # 64 
  
          A = (A + a) & 0xffffffffL
          B = (B + b) & 0xffffffffL
          C = (C + c) & 0xffffffffL
          D = (D + d) & 0xffffffffL
  
          self.A, self.B, self.C, self.D = A, B, C, D