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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _readhex(self, length, start):
 """Read bits and interpret as a hex string."""

        if length % 4:
            raise InterpretError("Cannot convert to hex unambiguously - "
                                           "not multiple of 4 bits.")
        if not length:
            return ''
        s = self._slice(start, start + length).tobytes()
        try:
            s = s.hex() # Available in Python 3.5
        except AttributeError:
            # This monstrosity is the only thing I could get to work for both 2.6 and 3.1.
            # TODO: Is utf-8 really what we mean here?
            s = str(binascii.hexlify(s).decode('utf-8'))
        # If there's one nibble too many then cut it off
        return s[:-1] if (length // 4) % 2 else s