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: command.rb
    path of file: ./repos/birdwatcher/lib/birdwatcher
    
    the code of the file until where you have to start completion: module Birdwatcher
  class Command
    class Error < StandardError; end
    class InvalidMetadataError < Error; end
    class MetadataNotSetError < Error; end

    ARGUMENT_SEPARATOR = " ".freeze

    attr_reader :arguments

    include Birdwatcher::Concerns::Core
    include Birdwatcher::Concerns::Util
    include Birdwatcher::Concerns::Outputting
    include Birdwatcher::Concerns::Presentation
    include Birdwatcher::Concerns::Persistence
    include Birdwatcher::Concerns::Concurrency

    def self.meta
      @meta || fail(MetadataNotSetError, "Metadata has not been set")
    end

    def self.meta=(meta)
      validate_metadata(meta)
      @meta = meta
    end

    def self.det
    
    def self.detailed_usage; end

    def self.descendants
      ObjectSpace.each_object(Class).select { |klass| klass < self }
    end

    def self.has_name?(name)
      meta[:names].include?(name)
    end

    def self.auto_completion_strings
      (meta[:names] + auto_completion).uniq
    end

    def self.auto_completion
      []
    end

    def execute(argument_line)
      @arguments = argument_line.to_s.split(ARGUMENT_SEPARATOR).map { |a| a.to_s.strip }
      run
    rescue => e
      error("#{e.class}".bold + ": #{e.message}")
      puts e.backtrace.join("\n")
    end

    protected

    def run
      fail NotImplementedError, "Commands must implement #run method"
    end

    def arguments?
      !arguments.empty?
    end

    def commands
      Birdwatcher::Command.descendants
    end

    def self.validate_metadata(meta)
      fail InvalidMetadataError, "Metadata is not a hash" unless meta.is_a?(Hash)
      fail InvalidMetadataError, "Metadata is empty" if meta.empty?
      fail InvalidMetadataError, "Metadata is missing key: description" unless meta.key?(:description)
      fail InvalidMetadataError, "Metadata is missing key: names" unless meta.key?(:names)
      fail InvalidMetadataError, "Metadata is missing key: usage" unless meta.key?(:usage)
      fail InvalidMetadataError, "Metadata names is not an array" unless meta[:names].is_a?(Array)
      fail InvalidMetadataError, "Metadata names must contain at least one string" if meta[:names].empty?
      fail InvalidMetadataError, "Metadata usage is not string" unless meta[:usage].is_a?(String)
    end
  end