Extract metadata element
extract_metadata_element(metadata, name = "name", empty = "<display>")the value of the metadata element, or "" if not found
m <- c(foo = "abc", bar = "def")
extract_metadata_element(m, name = "foo")
#> [1] "abc"
extract_metadata_element(m, name = "bar", empty = "def") ## return ""
#> [1] ""