<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def preprocess_worksheet(self, table, worksheet):
        '''
        Performs a preprocess pass of the table to attempt naive conversions of data and to record
        the initial types of each cell.
        '''
        table_conversion = []
        flags = {}
        units = {}
        for rind, row in enumerate(table):
            conversion_row = []
            table_conversion.append(conversion_row)
            if self.skippable_rows and worksheet in self.skippable_rows and rind in self.skippable_rows[worksheet]:
                self.flag_change(flags, 'interpreted', (rind, None), worksheet, self.FLAGS['skipped-row'])
                continue
            for cind, cell in enumerate(row):
                position = (rind, cind)
                if self.skippable_columns and worksheet in self.skippable_columns and cind in self.skippable_columns[worksheet]:
                    conversion = None
                    self.flag_change(flags, 'interpreted', position, worksheet, self.FLAGS['skipped-column'])
                else:
                    # Do the heavy lifting in pre_process_cell
                    conversion = auto_convert_cell(self, cell, position, worksheet, flags, units,
                            parens_as_neg=self.parens_as_neg)
                conversion_row.append(conversion)
        # Give back our conversions, type labeling, and conversion flags
        return table_conversion, flags, units