def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def inc_c(self, ind):
        r, c = self.row_col(ind)
        c += 1
        if c == self.nc:
            c = 0
        if r == (self.nr - 1) and c == (self.nc - 1):
            c = 0
        return self.indx(r, c)