'Args:
template_str: The template string.
undefined_str: A string to appear in the output when a variable to be
substituted is missing.  If None, UndefinedVariable is raised.
(Note: This is not really a compilation option, because affects
template expansion rather than compilation.  Nonetheless we make it a
constructor argument rather than an .expand() argument for
simplicity.)
It also accepts all the compile options that CompileTemplate does.'

def __init__(self, template_str, builder=None, undefined_str=None, **compile_options):

    self._program = CompileTemplate(template_str, builder=builder, **compile_options)
    self.undefined_str = undefined_str
