One Checker [extra Quality] [2026]

def check_one_to_one_relationship(self, left_data: List, right_data: List, left_key: str, right_key: str) -> OneCheckReport: """Check that relationships are one-to-one, not one-to-many""" left_keys = [item[left_key] for item in left_data] right_keys = [item[right_key] for item in right_data] # Check if any left key maps to multiple right items from collections import Counter right_counts = Counter(right_keys) violations = [] for key in set(left_keys): if right_counts.get(key, 0) > 1: violations.append({ 'key': key, 'count': right_counts[key] }) if violations: return OneCheckReport( check_name="One-to-one relationship check", result=CheckerResult.FAIL, message=f"Found {len(violations)} keys with multiple relationships", details={'violations': violations} ) else: return OneCheckReport( check_name="One-to-one relationship check", result=CheckerResult.PASS, message="All relationships are one-to-one" )

return CheckResponse( is_unique=len(duplicates) == 0, duplicates=duplicates, total_items=len(request.data), unique_count=len(seen) ) one checker

I'll help you develop a "one checker" feature. Since the requirements are open-ended, I'll create a that verifies if something is "one" (unique, consistent, singular) across a system. right_key: str) -&gt

def clean_check(): return passing_checker.check_unique_primary_key(clean_data, 'id') OneCheckReport: """Check that relationships are one-to-one