Rogue waves, bright–dark solitons and traveling wave solutions of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="mml81" display="inline" overflow="scroll" altimg="si81.gif"><mml:mrow><mml:mo>(</mml:mo><mml:mn>3</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:math>-dimensional generalized Kadomtsev–Petviashvili equation