def _pv_required(opts, key, is_required=true)
        if is_required
          if (opts.has_key?(key.to_s) && !opts[key.to_s].nil?) ||
              (opts.has_key?(key.to_sym) && !opts[key.to_sym].nil?)
            true
          else
            raise ValidationFailed, "Required argument #{key} is missing!"
          end
        end
      end
def _pv_required(opts, key, is_required=true)
        if is_required
          if (opts.has_key?(key.to_s) && !opts[key.to_s].nil?) ||
              (opts.has_key?(key.to_sym) && !opts[key.to_sym].nil?)
            true
          else
            raise ValidationFailed, "Required argument #{key} is missing!"
          end
        end
      end
Raise an exception if the parameter is not found.