Look up the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for a ValidatorHandler to recognize a feature name but temporarily be unable to return its value. Some feature values may be available only in specific contexts, such as before, during, or after a validation.

Implementors are free (and encouraged) to invent their own features, using names built on their own URIs.

Parameters:

name The feature name, which is a non-null fully-qualified URI.

Returns: The current value of the feature (true or false).

Exceptions:

SAXNotRecognizedException     If the feature value can't be assigned or retrieved.

SAXNotSupportedException     When the ValidatorHandler recognizes the feature name but cannot determine its value at this time.

NullPointerException     When name is null.

`SAXNotRecognizedException`		If the feature value can't be assigned or retrieved.
`SAXNotSupportedException`		When the `ValidatorHandler` recognizes the feature name but cannot determine its value at this time.
`NullPointerException`		When `name` is `null`.