    # File lib/core/facets/enumerable/graph.rb, line 12
      def graph(&yld)
        if yld
          h = {}
          each do |*kv|
            r = yld[*kv]
            case r
            when Hash
              nk, nv = *r.to_a[0]
            when Range
              nk, nv = r.first, r.last
            else
              nk, nv = *r
            end
            h[nk] = nv
          end
          h
        else
          Enumerator.new(self,:graph)
        end
      end