Adds a pattern to the generator
public function addPattern( string $pattern, bool $override, ): int;
If the pattern has the same skeleton as an existing pattern, and the override parameter is set, then the previous value is overridden. Otherwise, the previous value is retained. Note that single-field patterns (like "MMM") are automatically added, and don't need to be added explicitly!
string $pattern- Input pattern, such as "dd/MMM"
bool $override- When existing values are to be overridden use true, otherwise use false.
int- - pattern conflict status (see constants)