Unless the city avails itself of the general laws relative to the assessment and collection of city taxes by county officers, at the first regular meeting in July the legislative body shall sit as a board of equalization, and continue in session from day to day until all returns of the assessor have been rectified. It shall hear complaints, and correct, modify, or strike out any assessment made by the assessor. Of its own motion it may raise any assessment, after notice to the person whose assessment is to be raised.