code: def _render(template, callable_, args, data, as_unicode=False):
      
  
      if as_unicode:
          buf = util.FastEncodingBuffer(as_unicode=True)
      elif template.bytestring_passthrough:
          buf = compat.StringIO()
      else:
          buf = util.FastEncodingBuffer(
                          as_unicode=as_unicode,
                          encoding=template.output_encoding,
                          errors=template.encoding_errors)
      context = Context(buf, **data)
      context._outputting_as_unicode = as_unicode
      context._set_with_template(template)
  
      _render_context(template, callable_, context, *args,
                              **_kwargs_for_callable(callable_, data))
      return context._pop_buffer().getvalue()
docs: create a Context and return the string
      output of the given template and template callable.