def _parseHeader(self, data):
        # Note that each field of `self.header`, except for `payload_len`,
        # should already be set.
        already_parsed = (self.header.circ_id,
                          self.header.cmd,
                          self.header.link_version)
        for field in already_parsed:
            assert field is not None

        if 3 <= self.header.link_version:
            start = DEF.PAYLOAD_START_V3
        else:
            start = DEF.PAYLOAD_START_V4

        end = start + DEF.PAYLOAD_FIELD_LEN
        length = struct.unpack("!H", data[start:end])[0]
        self.header.payload_len = length
dataset/ETHPy150Open nskinkel/oppy/oppy/cell/varlen.py/VarLenCell._parseHeader/swapped operands of `<=`