How to use the openpyxl.cell.column_index_from_string function in openpyxl

:type column: int

        :rtype: tuples of tuples of :class:`openpyxl.cell.Cell`

        """
        if ':' in range_string:
            # R1C1 range
            result = []
            min_range, max_range = range_string.split(':')
            min_col, min_row = coordinate_from_string(min_range)
            max_col, max_row = coordinate_from_string(max_range)
            if column:
                min_col = get_column_letter(
                        column_index_from_string(min_col) + column)
                max_col = get_column_letter(
                        column_index_from_string(max_col) + column)
            min_col = column_index_from_string(min_col)
            max_col = column_index_from_string(max_col)
            cache_cols = {}
            for col in xrange(min_col, max_col + 1):
                cache_cols[col] = get_column_letter(col)
            rows = xrange(min_row + row, max_row + row + 1)
            cols = xrange(min_col, max_col + 1)
            for row in rows:
                new_row = []
                for col in cols:
                    new_row.append(self.cell('%s%s' % (cache_cols[col], row)))
                result.append(tuple(new_row))
            return tuple(result)
        else:
            try:
                return self.cell(coordinate=range_string, row=row,

def get_range_boundaries(range_string, row_offset=0, column_offset=1):

    if ':' in range_string:
        min_range, max_range = range_string.split(':')
        min_col, min_row = coordinate_from_string(min_range)
        max_col, max_row = coordinate_from_string(max_range)

        min_col = column_index_from_string(min_col)
        max_col = column_index_from_string(max_col) + 1

    else:
        min_col, min_row = coordinate_from_string(range_string)
        min_col = column_index_from_string(min_col)
        max_col = min_col + column_offset
        max_row = min_row + row_offset

    return (min_col, min_row, max_col, max_row)

:rtype: tuples of tuples of :class:`openpyxl.cell.Cell`

        """
        if ':' in range_string:
            # R1C1 range
            result = []
            min_range, max_range = range_string.split(':')
            min_col, min_row = coordinate_from_string(min_range)
            max_col, max_row = coordinate_from_string(max_range)
            if column:
                min_col = get_column_letter(
                        column_index_from_string(min_col) + column)
                max_col = get_column_letter(
                        column_index_from_string(max_col) + column)
            min_col = column_index_from_string(min_col)
            max_col = column_index_from_string(max_col)
            cache_cols = {}
            for col in xrange(min_col, max_col + 1):
                cache_cols[col] = get_column_letter(col)
            rows = xrange(min_row + row, max_row + row + 1)
            cols = xrange(min_col, max_col + 1)
            for row in rows:
                new_row = []
                for col in cols:
                    new_row.append(self.cell('%s%s' % (cache_cols[col], row)))
                result.append(tuple(new_row))
            return tuple(result)
        else:
            try:
                return self.cell(coordinate=range_string, row=row,
                        column=column)

msg = "You have to provide a value either for "\
                      "'coordinate' or for 'start_row', 'start_column', 'end_row' *and* 'end_column'"
                raise InsufficientCoordinatesException(msg)
            else:
                range_string = '%s%s:%s%s' % (get_column_letter(start_column + 1), start_row + 1, get_column_letter(end_column + 1), end_row + 1)
        elif len(range_string.split(':')) != 2:
            msg = "Range must be a cell range (e.g. A1:E1)"
            raise InsufficientCoordinatesException(msg)
        else:
            range_string = range_string.replace('$', '')

        if range_string in self._merged_cells:
            self._merged_cells.remove(range_string)
            min_col, min_row = coordinate_from_string(range_string.split(':')[0])
            max_col, max_row = coordinate_from_string(range_string.split(':')[1])
            min_col = column_index_from_string(min_col)
            max_col = column_index_from_string(max_col)
            # Mark cell as unmerged
            for col in xrange(min_col, max_col + 1):
                for row in xrange(min_row, max_row + 1):
                    if not (row == min_row and col == min_col):
                        self._get_cell('%s%s' % (get_column_letter(col), row)).merged = False
        else:
            msg = 'Cell range %s not known as merged.' % range_string
            raise InsufficientCoordinatesException(msg)

def write_worksheet_sheetviews(doc, worksheet):
    start_tag(doc, 'sheetViews')
    start_tag(doc, 'sheetView', {'workbookViewId': '0'})
    selectionAttrs = {}
    topLeftCell = worksheet.freeze_panes
    if topLeftCell:
        colName, row = coordinate_from_string(topLeftCell)
        column = column_index_from_string(colName)
        pane = 'topRight'
        paneAttrs = {}
        if column > 1:
            paneAttrs['xSplit'] = str(column - 1)
        if row > 1:
            paneAttrs['ySplit'] = str(row - 1)
            pane = 'bottomLeft'
            if column > 1:
                pane = 'bottomRight'
        paneAttrs.update(dict(topLeftCell=topLeftCell,
                              activePane=pane,
                              state='frozen'))
        tag(doc, 'pane', paneAttrs)
        selectionAttrs['pane'] = pane
        if row > 1 and column > 1:
            tag(doc, 'selection', {'pane': 'topRight'})

def get_highest_column(self):
        """Get the largest value for column currently stored.

        :rtype: int
        """
        if self.column_dimensions:
            return max([column_index_from_string(column_index)
                            for column_index in self.column_dimensions])
        else:
            return 1

def row_sort(cell):
    """Translate column names for sorting."""
    return column_index_from_string(cell.column)

def get_cells(self, min_row, min_col, max_row, max_col):
        p = iterparse(self.xml_source, tag=[ROW_TAG], remove_blank_text=True)
        for _event, element in p:
            if element.tag == ROW_TAG:
                row = int(element.get("r"))
                if max_row is not None and row > max_row:
                    break
                if min_row <= row:
                    for cell in safe_iterator(element, CELL_TAG):
                        coord = cell.get('r')
                        column_str, row = coordinate_from_string(coord)
                        column = column_index_from_string(column_str)
                        if max_col is not None and column > max_col:
                            break
                        if min_col <= column:
                            data_type = cell.get('t', 'n')
                            style_id = cell.get('s')
                            formula = cell.findtext(FORMULA_TAG)
                            value = cell.findtext(VALUE_TAG)
                            if formula is not None and not self.parent.data_only:
                                data_type = Cell.TYPE_FORMULA
                                value = "=%s" % formula
                            yield ReadOnlyCell(row, column_str, value, data_type,
                                          style_id)
            if element.tag in (CELL_TAG, VALUE_TAG, FORMULA_TAG):
                # sub-elements of rows should be skipped
                continue
            element.clear()

:param row_offset: additional rows (e.g. 4)
        :type row: int

        :param column_offset: additonal columns (e.g. 3)
        :type column: int

        :rtype: generator

        """
        if range_string:
            min_col, min_row, max_col, max_row = get_range_boundaries(range_string, row_offset, column_offset)
        else:
            min_col = column_index_from_string(self.min_col)
            max_col = self.max_col
            if max_col is not None:
                max_col = column_index_from_string(self.max_col) + 1
            min_row = self.min_row
            max_row = self.max_row

        return self.get_squared_range(min_col, min_row, max_col, max_row)