code: def uni_char_code(a: str, b: str, c: str, d: str):
      
      return char2hex(a) << 12 | char2hex(b) << 8 | char2hex(c) << 4 | char2hex(d)
docs: Convert unicode characters to integers.
  
      Converts four hexadecimal chars to the integer that the string represents.
      For example, uni_char_code('0','0','0','f') will return 15,
      and uni_char_code('0','0','f','f') returns 255.
  
      Returns a negative number on error, if a char was invalid.
  
      This is implemented by noting that char2hex() returns -1 on error,
      which means the result of ORing the char2hex() will also be negative.