Read a notebook represented as text

def reads(self, s, **_):
        """Read a notebook represented as text"""
        if self.fmt.get('format_name') == 'pandoc':
            return md_to_notebook(s)

        lines = s.splitlines()

        cells = []
        metadata, jupyter_md, header_cell, pos = header_to_metadata_and_cell(lines,
                                                                             self.implementation.header_prefix,
                                                                             self.implementation.extension)
        default_language = default_language_from_metadata_and_ext(metadata, self.implementation.extension)
        self.update_fmt_with_notebook_options(metadata)

        if header_cell:
            cells.append(header_cell)

        lines = lines[pos:]

        if self.implementation.format_name and self.implementation.format_name.startswith('sphinx'):
            cells.append(new_code_cell(source='%matplotlib inline'))

        cell_metadata = set()

        while lines:
            reader = self.implementation.cell_reader_class(self.fmt, default_language)
            cell, pos = reader.read(lines)
            cells.append(cell)
            cell_metadata.update(cell.metadata.keys())
            if pos <= 0:
                raise Exception('Blocked at lines ' + '\n'.join(lines[:6]))  # pragma: no cover
            lines = lines[pos:]

        update_metadata_filters(metadata, jupyter_md, cell_metadata)
        set_main_and_cell_language(metadata, cells, self.implementation.extension)

        if self.implementation.format_name and self.implementation.format_name.startswith('sphinx'):
            filtered_cells = []
            for i, cell in enumerate(cells):
                if cell.source == '' and i > 0 and i + 1 < len(cells) \
                        and cells[i - 1].cell_type != 'markdown' and cells[i + 1].cell_type != 'markdown':
                    continue
                filtered_cells.append(cell)
            cells = filtered_cells

        return new_notebook(cells=cells, metadata=metadata)