def namespace=(a_namespace)
      a_namespace = a_namespace.to_s
      SDL4R.validate_identifier(a_namespace) unless a_namespace.empty?
      @namespace = a_namespace
    end
def namespace=(a_namespace)
      a_namespace = a_namespace.to_s
      SDL4R.validate_identifier(a_namespace) unless a_namespace.empty?
      @namespace = a_namespace
    end
The namespace to set. +nil+ will be coerced to the empty string.

 Raises +ArgumentError+ if the namespace is non-blank and is not
 a legal SDL identifier (see SDL4R#validate_identifier)