code: def add_contributor(str, role = "A01")
        contrib = ::ONIX::Contributor.new
        contrib.sequence_number = product.contributors.size + 1
        contrib.contributor_role = role
        contrib.person_name_inverted = str
        product.contributors << contrib
      end
docs: set a new contributor to this product
   str should be the contributors name inverted (Healy, James)