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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def GetSource(self, row, col, table=None):
 """Return the source string of a cell"""


        if table is None:
            table = self.grid.current_table

        value = self.code_array((row, col, table))

        if value is None:
            return u""
        else:
            return value