code: def copy_and_sum_families(family_source, family_target):
      
      for every in family_source:
          if every not in family_target:
              family_target[every] = family_source[every]
          else:
              family_target[every] += family_source[every]
docs: 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