code: public static GrammaticalRelation getPrepC(String prepositionString) {
      GrammaticalRelation result = prepsC.get(prepositionString);
      if (result == null) {
        synchronized(prepsC) {
          result = prepsC.get(prepositionString);
          if (result == null) {
            result = new GrammaticalRelation(Language.English, "prepc", "prepc_collapsed", null, DEPENDENT, prepositionString);
            prepsC.put(prepositionString, result);
            threadSafeAddRelation(result);
          }
        }
      }
      return result;
    }
docs: The "prepc" grammatical relation. Used to collapse preposition
  complements.<p>
  They will be turned into prep_word, where "word" is a preposition
  
  NOTE: Because these relations lack associated GrammaticalRelationAnnotations,
  they cannot be arcs of a TreeGraphNode.
  
  @param prepositionString The preposition to make a GrammaticalRelation out of
  @return A grammatical relation for this preposition