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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 split_(self, col: str) -> "list(Ds)": """ Split the main dataframe according to a column's unique values and return a dict of dataswim instances :return: list of dataswim instances :rtype: list(Ds) :example: ``dss = ds.slit_("Col 1")`` """

        try:
            dss = {}
            unique = self.df[col].unique()
            for key in unique:
                df2 = self.df.loc[self.df[col] == key]
                ds2 = self._duplicate_(df2)
                dss[key] = ds2
            return dss
        except Exception as e:
            self.err(e, "Can not split dataframe")