function set( v ) {
	/* eslint-disable no-invalid-this */
	var isNum = isNumber( v );
	var i;
	if ( !isNum && !isNumberArray( v ) ) {
		throw new TypeError( format( 'invalid assignment. `%s` must be a number or an array of numbers. Value: `%s`.', 'lineOpacity', v ) );
	}
	if ( isNum ) {
		v = [ v ];
	} else {
		v = v.slice();
	}
	for ( i = 0; i < v.length; i++ ) {
		if ( v[ i ] < 0.0 || v[ i ] > 1.0 ) {
			throw new RangeError( format( 'invalid assignment. A `%s` must be a number on the interval: [0, 1]. Value: `%f`.', 'lineOpacity', v[i] ) );
		}
	}
	debug( 'Current value: %s.', JSON.stringify( this._lineOpacity ) );

	this._lineOpacity = v;
	debug( 'New Value: %s.', JSON.stringify( this._lineOpacity ) );

	this.emit( 'change' );
}
Sets the line opacity.

@private
@param {(number|NumberArray)} v - opacity
@throws {TypeError} must be a number or number array
@throws {RangeError} must be a number on the interval `[0,1]`