def measurement_set(type, value, unit)
      measure = measurement(type)

      # create a new isbn record if we need to
      if measure.nil?
        measure = ONIX::Measure.new
        measure.measure_type_code = type
        product.measurements << measure
      end

      # store the new value
      measure.measurement = value
      measure.measure_unit_code = unit.to_s
    end
def measurement_set(type, value, unit)
      measure = measurement(type)

      # create a new isbn record if we need to
      if measure.nil?
        measure = ONIX::Measure.new
        measure.measure_type_code = type
        product.measurements << measure
      end

      # store the new value
      measure.measurement = value
      measure.measure_unit_code = unit.to_s
    end
set the value of a particular measurement