# File lib/nanoc/extra/link_collector.rb, line 9
    def initialize(filenames, mode=nil)
      @filenames = filenames
      @filter = case mode
        when nil
          lambda { |h| true }
        when :external
          lambda { |h| external_href?(h) }
        when :internal
          lambda { |h| !external_href?(h) }
        else
          raise ArgumentError, 'Expected mode argument to be :internal, :external or nil'
        end 
    end