public String removeValue(Field field) {
        return removeValue(field.getName());
    }
Removes (undefines) the value of the given field returning its previous
value. If the field value was not defined, this function has no effect,
and null is returned.

@param field
    The field whose value should be removed.

@return
    The previous value of the field, or null if the value of the field
    was not previously defined.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/credentials/UserCredentials.java