<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def readat(self, off):
 """ Read all bytes from the start of `off` until the end of the buffer This method can be used to determine a checksum of a buffer from a given point on. :param int off: starting offset :rtype: bytearray """

        if isinstance(off, SV):
            off = off.value

        return self.__buff[off:]