The term discipline describes psychological restraining, with the use of rules and punishment to control overt behavior. It may be regarded as taboo or unnatural, and is a criminal offense in some countries, punishable by corporal or capital punishment; by contrast, people also regard anal sex as a natural and valid form of sexual activity that may be as equally fulfilling as any other desired sexual expression. Especially popular in post-World War 2 Japanese culture. However, the tradition of bondage magazines continues in the form of art books of bondage photographs, published by mainstream publishers such as Taschen. Given the wide range of practices, some of which may be engaged in by people who do not consider themselves as practicing BDSM, inclusion in the BDSM community or subculture is usually dependent on self-identification and shared experience. Others may also use vibrators and other sexual devices more commonly associated with female masturbation. He talked to them extensively on camera so that both he and the viewer can come to know them before any sex scenes. The name of the practice, when it is done in a repeated in-and-out motion, is derived from its passing resemblance to the dipping of a tea bag into a cup of hot water as a method of brewing tea. Failure to honor a safeword is considered serious misconduct and could even change the sexual consent situation into a crime, depending on the relevant law, since the bottom has explicitly revoked his or her consent to any actions that follow the use of the safeword . Fisting involves the insertion of one partner entire hand into a vagina or the anal cavity. Lesbianism gay video has been a theme in erotic art since at least the time of ancient Rome, and many regard depictions of lesbianism to be erotic. A variation on this is to place the fingers and thumb on the penis as if playing a flute, and then shuttle them back and forth. Lesbian pornography made for women is usually made by women, and usually features women who identify as lesbian or bisexual.