Best thing to do would be to track down the breeder and ask what the parents were. Other then that we can only guess by this picture. I think that there's a small chance it's a Black Pastel Ghost but it's very hard to tell and without seeing it in real life or knowing the parents it'll be hard to tell with that particular snake due to the very universal looking patterning. As the others have mentioned it also looks like it's a Lesser (probably the case).