Write docstrings for dataset generators

[kiudee]

Dataset generators like

cs-ranking/csrank/dataset_reader/choicefunctions/choice_data_generator.py

Lines 8 to 17 in 229d5dd

	class ChoiceDatasetGenerator(SyntheticDatasetGenerator):
	def __init__(self, dataset_type='pareto', **kwargs):
	super(ChoiceDatasetGenerator, self).__init__(
	learning_problem=CHOICE_FUNCTION, **kwargs)
	dataset_function_options = {'linear': self.make_latent_linear_choices,
	"pareto": self.make_globular_pareto_choices}
	if dataset_type not in dataset_function_options.keys():
	dataset_type = "pareto"
	self.dataset_function = dataset_function_options[dataset_type]

inherit the docstring of the parent class, which is not very informative.