code: public static Node getFirstNode(String mathml) {
          try {
              // get the apply node of the ContentMathML root
              return getFirstNode(new CMMLInfo(mathml));
          } catch (Exception e) {
              logger.error("failed to get apply node", e);
              return null;
          }
      }
docs: Get the first node of the MathML-Content annotations within a MathML document.
  
  @param mathml full MathML document
  @return first node of the MathML-Content annotations within a MathML document