Question: In what county is the city where Piner High School is located?

full_context: Document 1: Rosenberg's Department Store: Rosenberg's Department Store is located at Fourth and D Streets in downtown Santa Rosa, California. The structure is the most significant example of the Streamline Moderne style in Santa Rosa, and was the tallest building in the city for many years.
Document 2: Elsie Allen High School: Elsie Allen High School (EAHS) is a high school located in Santa Rosa, California at 599 Bellevue Ave. It is part of the Santa Rosa High School District, which is itself part of Santa Rosa City Schools. The primary feeder school is Cook Middle School. The school is named after Elsie Allen.
Document 3: Montgomery High School (Santa Rosa, California): Montgomery High School is a public high school located in Santa Rosa, California. It is part of the Santa Rosa High School District, which is itself part of Santa Rosa City Schools. The current principal is Randolph T. Burbank
Document 4: Graton, California: Graton is an unincorporated town and census-designated place (CDP) in west Sonoma County, California, United States. The population was 1,707 at the 2010 census. Graton's ZIP code is 95444. The town also has a culinary reputation attributed to two restaurants in the area.
Document 5: Santa Rosa, California: Santa Rosa is a city in and the county seat of Sonoma County, California, United States. Its estimated 2014 population was 174,170. Santa Rosa is the largest city in California's Redwood Empire, Wine Country and the North Bay; the fifth most populous city in the San Francisco Bay Area after San Jose, San Francisco, Oakland, and Fremont; and the 28th most populous city in California.
Document 6: Santa Rosa Creek Reservoir: Santa Rosa Creek Reservoir is a reservoir in Spring Lake Regional Park in the city of Santa Rosa, California, USA. It is impounded by an earthen dam built in 1963 and owned by the Sonoma County Water Agency.
Document 7: Cardinal Newman High School (Santa Rosa, California): Cardinal Newman High School is an American Catholic high school located in Santa Rosa, California. The school was originally for boys, but shared some facilities with Ursuline High School for girls; it has been coeducational since Ursuline's closure in 2011. The current principal is Graham Rutherford. Its colors are Cardinal Red and Gold; its mascot is the cardinal. It is located in the Roman Catholic Diocese of Santa Rosa in California.
Document 8: Piedmont Hills High School: Piedmont Hills High School is a comprehensive public four-year high school located in the Berryessa neighborhood of San Jose, California, USA. It is part of the East Side Union High School District and is the second highest performing school in the district, based on California's Academic Performance Index. It is currently a California Distinguished School and has received various awards in several aspects of its curriculum. Together with Independence High School and Yerba Buena High School, Piedmont Hills is one of a few schools in the district to have its own music program.
Document 9: Rosemont High School: Rosemont High School is a public high school located in Sacramento, California, USA. Designed by DLR Group, its completed buildings opened in 2003. Rosemont H.S. is part of the Sacramento City Unified School District.
Document 10: Santa Rosa Rugby Club: The Santa Rosa Rugby Club is a men's rugby union team based in and around Santa Rosa, California. The club was founded in 1971. The team plays in the Northern California Rugby Football Union at the Division I level. The Santa Rosa Rugby Club won back to back national championships in 1994-95.
Document 11: Piner High School: Piner High School (PHS) is a Public high school in Santa Rosa, California, United States. It is part of the Santa Rosa High School District, which is itself part of Santa Rosa City Schools.
Document 12: Santa Rosa, California: Santa Rosa (lit. Spanish for ``Saint Rose '') is a city in and the county seat of Sonoma County, in California's Wine Country. Its estimated 2016 population was 175,155. Santa Rosa is the largest city in California's Redwood Empire, Wine Country and the North Bay; the fifth most populous city in the San Francisco Bay Area after San Jose, San Francisco, Oakland, and Fremont; and the 28th most populous city in California.
Document 13: Santa Maria High School: Santa Maria High School (SMHS) is a public comprehensive high school in Santa Maria, California, United States. Located in the heart of the city, Santa Maria High School is the oldest school in the Santa Maria Valley and is part of the oldest high school district in California. The Santa Maria Joint Union High School District was founded on June 6, 1893.
Document 14: Naval Auxiliary Landing Field Santa Rosa: Naval Auxiliary Landing Field (NALF) Santa Rosa, California, also known as Naval Auxiliary Air Station, Santa Rosa, was a military airport located in Santa Rosa, California, in Sonoma County, California, USA.
Document 15: San Francisco: San Francisco (initials SF) (/ ˌsæn frənˈsɪskoʊ /, Spanish for Saint Francis; Spanish: (san franˈsisko)), officially the City and County of San Francisco, is the cultural, commercial, and financial center of Northern California. The consolidated city - county covers an area of about 47.9 square miles (124 km), mostly at the north end of the San Francisco Peninsula in the San Francisco Bay Area. It is the fourth-most populous city in California, and the 13th-most populous in the United States, with a 2016 census - estimated population of 870,887. The population is projected to reach 1 million by 2033. As of 2016, San Francisco County was the 7th highest - income county in the United States, with a per capita personal income of $110,418.
ground_truth: Sonoma County
sub_queries: Piner High School >> location Answer: Santa Rosa
what part of california is Santa Rosa in Answer: Sonoma County