code: def to_bb(YY, y="deprecated"):
      
      cols,rows = np.nonzero(YY)
      if len(cols)==0: return np.zeros(4, dtype=np.float32)
      top_row = np.min(rows)
      left_col = np.min(cols)
      bottom_row = np.max(rows)
      right_col = np.max(cols)
      return np.array([left_col, top_row, right_col, bottom_row], dtype=np.float32)
docs: Convert mask YY to a bounding box, assumes 0 as background nonzero object