function get() {
	/* eslint-disable no-invalid-this */
	if ( isString( this._tickFormat ) ) {
		return format( this._tickFormat );
	}
	if ( isNull( this._tickFormat ) ) {
		if ( this._scale.tickFormat ) {
			return this._scale.tickFormat( this._numTicks, this._tickFormat );
		}
		return identity;
	}
	return this._tickFormat;
}
Returns the axis tick format.

@private
@returns {Function} format function