'Create a worksheet (at an optional index).
:param index: optional position at which the sheet will be inserted
:type index: int'

def create_sheet(self, index=None):

    if self.__optimized_read:
        raise ReadOnlyWorkbookException('Cannot    create    new    sheet    in    a    read-only    workbook')
    if self.__optimized_write:
        new_ws = DumpWorksheet(parent_workbook=self)
    else:
        new_ws = Worksheet(parent_workbook=self)
    self.add_sheet(worksheet=new_ws, index=index)
    return new_ws
