def enable_tls(context = nil)
      if context && context.kind_of?(OpenSSL::SSL::SSLContext)
        true
      elsif context
        raise TypeError,
          "wrong argument (#{context.class})! "+
          "(Expected kind of OpenSSL::SSL::SSLContext)"
      end
    end
def enable_tls(context = nil)
      if context && context.kind_of?(OpenSSL::SSL::SSLContext)
        true
      elsif context
        raise TypeError,
          "wrong argument (#{context.class})! "+
          "(Expected kind of OpenSSL::SSL::SSLContext)"
      end
    end
in the standard lib: net/smtp.rb line 577
   a TypeError is thrown unless this arg is a
   kind of OpenSSL::SSL::SSLContext