docs: def hex_from(val):
      """Returns hex string representation for a given value.
  
      :param bytes|str|unicode|int|long val:
      :rtype: bytes|str
      """
      if isinstance(val, integer_types):
          hex_str = '%x' % val
          if len(hex_str) % 2:
              hex_str = '0' + hex_str
          return hex_str
  
      return hexlify(val)