Return a pandas DataFrame with entries sorted according to `sort_key`.

def get_dataframe(self, sort_key="wall_time", **kwargs):
        """
        Return a pandas DataFrame with entries sorted according to `sort_key`.
        """
        import pandas as pd
        frame = pd.DataFrame(columns=AbinitTimerSection.FIELDS)

        for osect in self.order_sections(sort_key):
            frame = frame.append(osect.to_dict(), ignore_index=True)

        # Monkey patch
        frame.info =  self.info
        frame.cpu_time =  self.cpu_time
        frame.wall_time =  self.wall_time
        frame.mpi_nprocs =  self.mpi_nprocs
        frame.omp_nthreads =  self.omp_nthreads
        frame.mpi_rank =  self.mpi_rank
        frame.fname =  self.fname

        return frame