'Class method to parse prefix node and return a Node.'

@classmethod
def handle_token(cls, parser, token, name):

    tokens = token.contents.split()
    if ((len(tokens) > 1) and (tokens[1] != 'as')):
        raise template.TemplateSyntaxError(("First    argument    in    '%s'    must    be    'as'" % tokens[0]))
    if (len(tokens) > 1):
        varname = tokens[2]
    else:
        varname = None
    return cls(varname, name)
