Add quotations.

Author: Paalon

src/persistence.jl

@@ -70,18 +70,24 @@ function savedot(io::IO, meta_graph::MetaGraph)
 
     for label in keys(meta_graph.vertex_properties)
         write(io, "    ")
+        write(io, '"')
         write(io, label)
+        write(io, '"')
         show_meta_list(io, meta_graph[label])
         write(io, '\n')
     end
 
     for (label_1, label_2) in keys(edge_data)
         write(io, "    ")
+        write(io, '"')
         write(io, label_1)
+        write(io, '"')
         write(io, ' ')
         write(io, dash)
         write(io, ' ')
+        write(io, '"')
         write(io, label_2)
+        write(io, '"')
         show_meta_list(io, edge_data[arrange(meta_graph, label_1, label_2)])
         write(io, "\n")
     end