Character. Which category of metadata to display. If
unspecified, function returns the categories of metadata available.
locale
Character. One of the supported two-letter ISO 639-1 language
codes. Current supported languages are English, Finnish and Swedish. For
data where more than one language is available the language denoted by
locale will be preferred while falling back to the other languages in the
order indicated above.
cache
Logical or Integer. If TRUE or a number greater than zero,
then data-caching will be used. If not logical then cache will be
invalidated after the number of hours indicated by the argument.