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: stream_keys.rs
    path of file: ./repos/databend/src/query/storages/common/table_meta/src/table
    
    the code of the file until where you have to start completion: // Copyright 2021 Datafuse Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Stream table options.
pub const OPT_KEY_TABLE_NAME: &str = "table_name";
pub const OPT_KEY_DATABASE_NAME: &str = "table_database";
pub const OPT_KEY_TABLE_ID: &str = "table_id";
pub const OPT_KEY_TABLE_VER: &str = "table_version";
pub con
    
pub fn get_change_type(table_alias_name: &Option<String>) -> Option<ChangeType> {
    let mut change_type = None;
    if let Some(table_alias) = table_alias_name {
        let alias_param = table_alias.split('$').collect::<Vec<_>>();
        if alias_param.len() == 2 && alias_param[1].len() == 8 {
            if let Ok(suffix) = i64::from_str_radix(alias_param[1], 16) {
                // 2023-01-01 00:00:00.
                let base_timestamp = 1672502400;
                if suffix > base_timestamp {
                    change_type = match alias_param[0] {
                        "_change_append" => Some(ChangeType::Append),
                        "_change_insert" => Some(ChangeType::Insert),
                        "_change_delete" => Some(ChangeType::Delete),
                        _ => None,
                    };
                }
            }
        }
    }
    change_type
}