518. Extortion is the obtaining of property from another, with his consent, or the obtaining of an official act of a public officer, induced by a wrongful use of force or fear, or under color of official right. 519. Fear, such as will constitute extortion, may be induced by a threat, either: 1. To do an unlawful injury to the person or property of the individual threatened or of a third person; or, 2. To accuse the individual threatened, or any relative of his, or member of his family, of any crime; or, 3. To expose, or to impute to him or them any deformity, disgrace or crime; or, 4. To expose any secret affecting him or them