function set( label ) {
	/* eslint-disable no-invalid-this */
	if ( !isString( label ) ) {
		throw new TypeError( format( 'invalid assignment. `%s` must be a string. Value: `%s`.', 'yLabel', label ) );
	}
	if ( label !== this._yLabel ) {
		debug( 'Current value: %s.', this._yLabel );

		this._yLabel = label;
		debug( 'New value: %s.', this._yLabel );

		this.emit( 'change' );
	}
}
Sets the y-axis label.

@private
@param {string} label - axis label
@throws {TypeError} must be a string