def list(search)
      @config.transaction do
        networks = @config.networks.dup
        unless search.nil?
          networks.select! { |net| net.name.downcase.include? search.downcase }
        end
        puts 'No networks found' if networks.empty?
        networks.each { |net| show_network net }
      end
    end
def list(search)
      @config.transaction do
        networks = @config.networks.dup
        unless search.nil?
          networks.select! { |net| net.name.downcase.include? search.downcase }
        end
        puts 'No networks found' if networks.empty?
        networks.each { |net| show_network net }
      end
    end
Lists all networks, or networks with names containing the given search
 term.

 @param search [String, nil] an optional search term