docs: def new(cls, num_id, abstractNum_id):
          """
          Return a new ``<w:num>`` element having numId of *num_id* and having
          a ``<w:abstractNumId>`` child with val attribute set to
          *abstractNum_id*.
          """
          num = OxmlElement('w:num')
          num.numId = num_id
          abstractNumId = CT_DecimalNumber.new(
              'w:abstractNumId', abstractNum_id
          )
          num.append(abstractNumId)
          return num