# File lib/feed-normalizer.rb, line 32
    def self.map_functions!(mapping, src, dest)

      mapping.each do |dest_function, src_functions|
        src_functions = [src_functions].flatten # pack into array

        src_functions.each do |src_function|
          value = if src.respond_to?(src_function)
            src.send(src_function)
          elsif src.respond_to?(:has_key?)
            src[src_function]
          end

          unless value.to_s.empty?
            append_or_set!(value, dest, dest_function)
            break
          end
        end

      end
    end