assert(self.support_handler.read((from_chain, from_handler)) && 
       self.support_handler.read((to_chain, contract_address_to_u256(to_handler))), 'not support handler');
fn set_support_handler(ref self: ContractState, chain_name: felt252, handler: u256, support: bool) {
    self.ownable.assert_only_owner();
    self.support_handler.write((chain_name, handler), support);
}
if (is_valid_handler(from_chain, from_handler) == false) {
    return false;
}
