methods iterates thru source family and copies its entries to target family
    in case key already exists in both families - then the values are added

def copy_and_sum_families(family_source, family_target):
    """ methods iterates thru source family and copies its entries to target family
    in case key already exists in both families - then the values are added"""
    for every in family_source:
        if every not in family_target:
            family_target[every] = family_source[every]
        else:
            family_target[every] += family_source[every]