def METHOD_NAME(portfolioWeights, list_of_portfolio_weights):
    list_of_unique_asset_names = list(
        set(
            flatten_list(
                [
                    list(subportfolio.keys())
                    for subportfolio in list_of_portfolio_weights
                ]
            )
        )
    )
    portfolio_weights = portfolioWeights.allzeros(list_of_unique_asset_names)
    for subportfolio_weights in list_of_portfolio_weights:
        for asset_name in list(subportfolio_weights.keys()):
            portfolio_weights[asset_name] = (
                portfolio_weights[asset_name] + subportfolio_weights[asset_name]
            )
    return portfolio_weights