code: private String processTemplate(Template template, Object model) {
          if (template != null) {
              StringWriter sw = new StringWriter();
              try {
                  template.process(model, sw);
              } catch (Exception e) {
                  throw new RuntimeException("Failed to process template " + e.getMessage());
              }
              return sw.toString();
          }
          return "";
      }
docs: Process a freemarker templates <code>template</code> with the model
  <code>classModel</code> and return the resulting strings. At this stage
  some informations of the class are updated in the <code>classModel</code>
  and these informations can be used inside the freemarker
  <code>template</code> to deduce the C++ source code. <br>
  Templates exemple :<br>
  <code>"std::vector<${innerType.type.cppReturnType} >"</code><br>
  <code>"${type.addInclude("&lt;vector>")}"</code>
  
  @param template
  a freemarker template for generating parts of C++ source code
  @param model
  a semi-filled <code>ClassModel</code>
  @return the freemarker template processing results