<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _string_to_byte_list(self, data):
 """ Creates a hex digest of the input string given to create the image, if it's not already hexadecimal Returns: Length 16 list of rgb value range integers (each representing a byte of the hex digest) """

        bytes_length = 16

        m = self.digest()
        m.update(str.encode(data))
        hex_digest = m.hexdigest()

        return list(int(hex_digest[num * 2:num * 2 + 2], bytes_length)
                    for num in range(bytes_length))