Check if a format is supported
is_valid_format(x, stop_otherwise = FALSE)
either format string or an object returned by sprintf_format
logical, if x
is not a format should an error be
thrown
TRUE
if x
is NULL
, a supported format string, or a function; FALSE
otherwise.
No check if the function is actually a formatter is performed.
is_valid_format("xx.x")
#> [1] TRUE
is_valid_format("fakeyfake")
#> [1] FALSE