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: position_file.rb
    path of file: ./repos/fluentd/lib/fluent/plugin/in_tail
    
    the code of the file until where you have to start completion: #
# Fluentd
#
#    Licensed under the Apache License, Version 2.0 (the "License");
#    you may not use this file except 
    
      def compact(existing_targets = nil)
        @file_mutex.synchronize do
          entries = fetch_compacted_entries
          @logger&.debug "Compacted entries: ", entries.keys

          if existing_targets
            entries = remove_deleted_files_entries(entries, existing_targets)
            @logger&.debug "Remove missing entries.",
                           existing_targets: existing_targets.keys,
                           entries_after_removing: entries.keys
          end

          @file.pos = 0
          @file.truncate(0)
          @file.write(entries.values.map(&:to_entry_fmt).join)
        end