code: protected <A> A getTypedParam(String paramName, String errorMessage, Class<A> clazz) throws IOException {
          return getTypedParam(paramName, errorMessage, clazz, (Map<String, Object>) inputParams.get());
      }
docs: Convenience method for subclasses. Uses the default parametermap for this deserializer.
  
  @param paramName    the name of the parameter
  @param errorMessage the errormessage to add to the exception if the param does not exist.
  @param clazz        the class of the parameter that should be parsed.
  @param <A>          the type of the parameter
  @return a stringparameter with given name. If it does not exist and the errormessage is provided,
  an IOException is thrown with that message. if the errormessage is not provided, null is returned.
  @throws IOException Exception if the paramname does not exist and an errormessage is provided.