def process(input, context=nil, filename=nil)
      code = convert(input)
      filename ||= '(erubis)'
      if context.is_a?(Binding)
        return eval(code, context, filename)
      else
        context = Context.new(context) if context.is_a?(Hash)
        return context.instance_eval(code, filename)
      end
    end
def process(input, context=nil, filename=nil)
      code = convert(input)
      filename ||= '(erubis)'
      if context.is_a?(Binding)
        return eval(code, context, filename)
      else
        context = Context.new(context) if context.is_a?(Hash)
        return context.instance_eval(code, filename)
      end
    end
helper method to convert and evaluate input text with context object.
 context may be Binding, Hash, or Object.