'Create an empty template.
Creates a new empty template with given version. If version is
not provided, a new empty HOT template of version "2015-04-30"
is returned.
:param version: A tuple containing version header of the
template: version key and value. E.g. ("heat_template_version",
"2015-04-30")
:returns: A new empty template.'

@classmethod
def create_empty_template(cls, version=('heat_template_version', '2015-04-30'), from_template=None):

    if from_template:
        tmpl = copy.deepcopy(from_template)
        tmpl.remove_all_resources()
        return tmpl
    else:
        tmpl = {version[0]: version[1]}
        return cls(tmpl)
