What is the test for establishing that a primary activity of a criminal gang is "primary activities"?

"The phrase 'primary activities,' as used in the gang statute, implies that the commission of one or more of the statutorily enumerated crimes is one of the group's 'chief' or 'principal' occupations. [Citation.]" (People v. Sengpadychith (2001) 26 Cal.4th 316, 323.) "Sufficient proof of the gang's primary activities might consist of evidence that the group's members consistently and repeatedly have committed criminal activity listed in the gang statute," and expert testimony (including that of a police gang expert) that the gang primarily engaged in some of the enumerated crimes, based on conversations with gang members, personal investigations, and information from law enforcement colleagues, would suffice. (Id. at p. 324.)