human
Complete this python program:
def MessageSetItemSizer(field_number):
assistant
#Here is the Python code you requested.

    """Returns a sizer for extensions of MessageSet.
    The message set message looks like this:
    message MessageSet {
    repeated group Item = 1 {
    required int32 type_id = 2;
    required string message = 3;
    """
    static_size = ((((_TagSize(1) * 2) + _TagSize(2)) + _VarintSize(field_number)) + _TagSize(3))
    local_VarintSize = _VarintSize
    def FieldSize(value):
        l = value.ByteSize()
        return ((static_size + local_VarintSize(l)) + l)
    return FieldSize