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: rpc_filter.rs
    path of file: ./repos/cita/cita-chain/core/src/filters
    
    the code of the file until where you have to start completion: // Copyright Rivtower Technologies LLC.
//
// 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.

use crate::libchain::chain::Chain;
use crate::types::block_number::{BlockNumber, BlockTag, Tag};
use crate::typ
    
    fn get_filter_changes(&self, id: usize) -> Option<FilterChanges> {
        let filterdb = self.filter_db();
        let mut changes = Some(FilterChanges::Empty);
        let current_number = self.get_current_height();
        let block_filter = self.get_block_filter(id);

        if !filterdb.try_lock().unwrap().is_filter(id) {
            drop(filterdb);
            return changes;
        }

        // Check the logs
        if let Some(filter) = filterdb.try_lock().unwrap().get_logs_filter(id) {
            trace!("Into filter changes: logs");
            changes = Some(FilterChanges::Logs(
                self.get_logs_with_filter(filter.clone(), block_filter),
            ));
        };

        // Check the block
        if filterdb.try_lock().unwrap().is_block_filter(id) {
            trace!("Into filter changes: block");
            // Return hashes from next block after the filter was created to the current block.
            let hashes = ((block_filter + 1)..=current_number)
                .filter_map(|_id| self.block_hash_by_height(_id))
                .collect::<Vec<H256>>();
            trace!("Block filter changes: {:?}", hashes);
            changes = Some(FilterChanges::Hashes(
                hashes.into_iter().map(Into::into).collect(),
            ));
        };

        // Update the block filter: use the current number
        filterdb
            .try_lock()
            .unwrap()
            .gen_block_filter(id, current_number);
        drop(filterdb);
        changes
    }