filter
Returns a possibly new FormatOptions instance possibly containing a subset of the formatting information. This is useful if a backend implementation wishes to create formatting options that ignore some of the specified formatting information.
Parameters
allowed Flags
A mask of flag values to be retained in the returned instance. Use ALL_FLAGS to retain all flag values, or 0 to suppress all flags.
allow Width
specifies whether to include width in the returned instance.
allow Precision
specifies whether to include precision in the returned instance.