You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: _rules_source_list.rs
    path of file: ./repos/aws-sdk-rust/sdk/networkfirewall/src/types
    
    the code of the file until where you have to start completion: // Code generated by software.amazon.smithy.rust.codegen.smithy-rs. DO NOT EDIT.

/// <p>Stateful inspection criteria for a domain list rule group.</p>
/// <p>For HTTPS traffic, domain filtering is SNI-based. It uses the server name indicator extension of the TLS handshake.</p>
/// <p>By default, Network Firewall domain list inspection only includes traffic coming from the VPC where you deploy the firewall. To inspect traffic from IP addresses outside of the deployment VPC, you set the <code>HOME_NET</code> rule variable to include the CIDR range of the deployment VPC plus the other CIDR ranges. For more information, see <code>RuleVariables</code> in this guide and <a href="https://docs.aws.amazon.com/network-firewall/latest/developerguide/stateful-rule-groups-domain-names.html">Stateful domain l
    
    pub fn build(self) -> ::std::result::Result<crate::types::RulesSourceList, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::RulesSourceList {
            targets: self.targets.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "targets",
                    "targets was not specified but it is required when building RulesSourceList",
                )
            })?,
            target_types: self.target_types.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "target_types",
                    "target_types was not specified but it is required when building RulesSourceList",
                )
            })?,
            generated_rules_type: self.generated_rules_type.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "generated_rules_type",
                    "generated_rules_type was not specified but it is required when building RulesSourceList",
                )
            })?,
        })
    }