Reduce cyclomatic complexity in experimental APIs

The functions below are too long and hamper readability.

Line 338 in a26bdb2

def generate_data_yaml(self):

Line 178 in a26bdb2

def __extract_class_initializing_args(self, class_name):

Line 72 in a26bdb2

def filter_attributes(ctx, f, **kwargs):

Line 161 in a26bdb2

def _parse(self, func_ast):

Line 322 in a26bdb2

def save_artifacts(self, artifacts_iter, force_v4=False, len_hint=0):

Suggestions:

Aim for a function size that fits within screen height (note that reducing comments or blank lines won't change the way formatter views complexity).
Break down large functions to smaller defs. These helper defs can be part of the same module.
Try reducing conditional branching

These changes are required to merge #1176.