def to_dict(self, save_data=True):
input_dict = super(SparseGP, self).to_dict(save_data)<EOL>input_dict["<STR_LIT:class>"] = "<STR_LIT>"<EOL>input_dict["<STR_LIT>"] = self.Z.tolist()<EOL>return input_dict<EOL>
Convert the object into a json serializable dictionary.

:param boolean save_data: if true, it adds the training data self.X and self.Y to the dictionary
:return dict: json serializable dictionary containing the needed information to instantiate the object