def convert(self, value, view):
        is_mapping = isinstance(self.template, MappingTemplate)

        for candidate in self.allowed:
            try:
                if is_mapping:
                    if isinstance(candidate, Filename) and \
                            candidate.relative_to:
                        next_template = candidate.template_with_relatives(
                            view,
                            self.template
                        )

                        next_template.subtemplates[view.key] = as_template(
                            candidate
                        )
                    else:
                        next_template = MappingTemplate({view.key: candidate})

                    return view.parent.get(next_template)[view.key]
                else:
                    return view.get(candidate)
            except ConfigTemplateError:
                raise
            except ConfigError:
                pass
            except ValueError as exc:
                raise ConfigTemplateError(exc)

        self.fail(
            u'must be one of {0}, not {1}'.format(
                repr(self.allowed), repr(value)
            ),
            view
        )
Ensure that the value follows at least one template.
dataset/ETHPy150Open beetbox/beets/beets/util/confit.py/OneOf.convert