code: def long_to_hex(l, size):
      
      f_str = "{0:0%sx}" % size
      return ensure_bytes(f_str.format(l).lower())
docs: Encode a long value as a hex string, 0-padding to size.
  
      Note that size is the size of the resulting hex string. So, for a 32Byte
      long size should be 64 (two hex characters per byte".