<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def process_mock_rpc(input_string):
 """Process a mock RPC argument. Args: input_string (str):
 The input string that should be in the format <slot id>:<rpc id> = value """


    spec, equals, value = input_string.partition(u'=')

    if len(equals) == 0:
        print("Could not parse mock RPC argument: {}".format(input_string))
        sys.exit(1)

    try:
        value = int(value.strip(), 0)
    except ValueError as exc:
        print("Could not parse mock RPC value: {}".format(str(exc)))
        sys.exit(1)

    slot, part, rpc_id = spec.partition(u":")
    if len(part) == 0:
        print("Could not parse mock RPC slot/rpc definition: {}".format(spec))
        sys.exit(1)

    try:
        slot = SlotIdentifier.FromString(slot)
    except ArgumentError as exc:
        print("Could not parse slot id in mock RPC definition: {}".format(exc.msg))
        sys.exit(1)

    try:
        rpc_id = int(rpc_id, 0)
    except ValueError as exc:
        print("Could not parse mock RPC number: {}".format(str(exc)))
        sys.exit(1)

    return slot, rpc_id, value