Add common APIs for settings datastore

        contentResolver.unregisterContentObserver(contentObserver)

    }

    /** Gets the boolean value of given key. */

    fun getBoolean(key: String): Boolean? = getValue(key, Boolean::class.javaObjectType)

    /** Sets boolean value for given key, null value means delete the key from data store. */

    fun setBoolean(key: String, value: Boolean?) =

        setValue(key, Boolean::class.javaObjectType, value)

    /** Gets the float value of given key. */

    fun getFloat(key: String): Float? = getValue(key, Float::class.javaObjectType)

    /** Sets float value for given key, null value means delete the key from data store. */

    fun setFloat(key: String, value: Float?) = setValue(key, Float::class.javaObjectType, value)

    /** Gets the int value of given key. */

    fun getInt(key: String): Int? = getValue(key, Int::class.javaObjectType)

    /** Sets int value for given key, null value means delete the key from data store. */

    fun setInt(key: String, value: Int?) = setValue(key, Int::class.javaObjectType, value)

    /** Gets the long value of given key. */

    fun getLong(key: String): Long? = getValue(key, Long::class.javaObjectType)

    /** Sets long value for given key, null value means delete the key from data store. */

    fun setLong(key: String, value: Long?) = setValue(key, Long::class.javaObjectType, value)

    /** Gets the string value of given key. */

    fun getString(key: String): String? = getValue(key, String::class.javaObjectType)

    /** Sets string value for given key, null value means delete the key from data store. */

    fun setString(key: String, value: String?) = setValue(key, String::class.javaObjectType, value)

    /** Tag for logging. */

    abstract val tag: String

}