Node name error

I just added a check in the node and edge names before outputting them. In the case of the names are reserved i just add a "_" in the beginning of them, the print is the same because the label still the same. I searched in the dot documentation for a list of reserved words but did't find it or the dot grammar, so i just used a list of the one's that i know. I tested with rake, that passed, but i had to skip sample 36.