docs: public JSONWriter keySymbolValuePair(String aKey, String aValue)
              throws JSONException {
          assert(aKey != null);
          assert(m_mode == 'k');
          // The key should not have already been seen in this scope.
          assert(m_scopeStack[m_top].add(aKey));
  
          try {
              m_writer.write(m_expectingComma ? ",\"" : "\"");
              m_writer.write(aKey);
  	        if (aValue == null) {
                  m_writer.write("\":null");
  	        }
  	        else {
                  m_writer.write("\":\"");
                  m_writer.write(JSONObject.quotable(aValue));
                  m_writer.write('"');
  	        }
          }
          catch (IOException e) {
              throw new JSONException(e);
          }
          m_expectingComma = true;
          return this;
      }