code: def make_nucsat(relname, nuc_types, elements):
      
      assert len(elements) == 2 and len(nuc_types) == 2, \
          "A nucsat relation must have two elements."
      assert set(nuc_types) == set(['N', 'S']), \
          "A nucsat relation must consist of one nucleus and one satellite."
   
      result = "\dirrel"
      for i, nuc_type in enumerate(nuc_types):
          if nuc_type == 'N':
              result += '\n\t' + NUC_TEMPLATE.substitute(nucleus=elements[i])    
          else:
              result += '\n\t' + SAT_TEMPLATE.substitute(satellite=elements[i], relation=relname)
      return result
docs: Creates a rst.sty Latex string representation of a standard RST relation
      (one nucleus, one satellite).