code: def encode_int(code, bits_per_char=6):
      
      if code < 0:
          raise ValueError('Only positive ints are allowed!')
  
      if bits_per_char == 6:
          return _encode_int64(code)
      if bits_per_char == 4:
          return _encode_int16(code)
      if bits_per_char == 2:
          return _encode_int4(code)
  
      raise ValueError('`bits_per_char` must be in {6, 4, 2}')
docs: Encode int into a string preserving order
  
      It is using 2, 4 or 6 bits per coding character (default 6).
  
      Parameters:
          code: int           Positive integer.
          bits_per_char: int  The number of bits per coding character.
  
      Returns:
          str: the encoded integer