Render a DataFrame to a console-friendly tabular output.

        Wrapper around the :meth:`pandas.DataFrame.to_string` method.

def to_string(self, buf=None, format_abs_ref_as='string',
                  upper_triangle=True, header=True, index=True, **kwargs):
        """Render a DataFrame to a console-friendly tabular output.

        Wrapper around the :meth:`pandas.DataFrame.to_string` method.
        """
        out = self._sympy_formatter()
        out = out._abs_ref_formatter(format_as=format_abs_ref_as)
        if not upper_triangle:
            out = out._remove_upper_triangle()

        content = out._frame.to_string(buf=buf, header=header, index=index,
                                       **kwargs)
        if not index and not header:
            # NOTE(the following might be removed in the future
            # introduced because of formatting bug in pandas
            # See https://github.com/pandas-dev/pandas/issues/13032)
            space = ' ' * (out.loc[:, 'atom'].str.len().max()
                           - len(out.iloc[0, 0]))
            content = space + content
        return content