changed font type in dot header to pure helvetica

src/optic_scenery.rs

@@ -149,9 +149,9 @@ impl OpticScenery {
         dot_string.push_str("\tcompound = true;\n");
         dot_string.push_str(&format!("\trankdir = \"{}\";\n", rankdir));
         dot_string.push_str(&format!("\tlabel=\"{}\"\n", self.description()));
-        dot_string.push_str("\tfontname=\"Helvetica,Arial,sans-serif\"\n");
-        dot_string.push_str("\tnode [fontname=\"Helvetica,Arial,sans-serif\" fontsize = 10]\n");
-        dot_string.push_str("\tedge [fontname=\"Helvetica,Arial,sans-serif\"]\n\n");
+        dot_string.push_str("\tfontname=\"Helvetica\"\n");
+        dot_string.push_str("\tnode [fontname=\"Helvetica\" fontsize = 10]\n");
+        dot_string.push_str("\tedge [fontname=\"Helvetica\"]\n\n");
         dot_string
     }
     fn create_node_edge_str(