code: public Property getProperty(String propertyName) {
          if (propertyName == null) {
              throw new NullPointerException("Cannot get a property with a 'null' propertyName.");
          }
  
          return properties.get(propertyName);
      }
docs: Returns a single public property of the analized class or interface,
  if present, else {@code null}.
  
  @param propertyName the name of the property to retrieve
  @return the {@link Property} searched, or {@code null} if not found
  @throws NullPointerException if propertyName parameter is {@code null}