Calculation including many child tables

Am new to coding , am trying to create a code that will multiply the self rating, excom rating and Mancom rating as seen in the code below . The code am sharing has not worked . Please help me get it right . Remember there two child tables . @ Usama_Naveed

total_rating_final = 0

for item in doc.kpi_structure:
    # Validate inputs
    if not all(isinstance(rating, (int, float)) for rating in [item.self_rating, item.mancom_rating, item.excom_rating]):
        continue  # Skip the item if ratings are not numbers

    # Ensure weight is valid to avoid division by zero
    if item.weight > 0:
        total_rating_final += (item.self_rating + item.mancom_rating + item.excom_rating) / 3 * (item.weight / 100)

# Assign the final total to the document without rounding
doc.total_rating_final = total_rating_finaltype or paste code here