<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def dataframe2sasdata(self, df: 'pd.DataFrame', table: str = '_df', libref: str = '', results: str = '', keep_outer_quotes: bool = False) -> 'SASdata': """ This method imports a Pandas Data Frame to a SAS Data Set, returning the SASdata object for the new Data Set. :param df: Pandas Data Frame to import to a SAS Data Set :param table: the name of the SAS Data Set to create :param libref: the libref for the SAS Data Set being created. Defaults to WORK, or USER if assigned :param results: format of results, SASsession.results is default, PANDAS, HTML or TEXT are the alternatives :param keep_outer_quotes: the defualt is for SAS to strip outer quotes from delimitted data. This lets you keep them :return: SASdata object """

        if libref != '':
           if libref.upper() not in self.assigned_librefs():
              print("The libref specified is not assigned in this SAS Session.")
              return None

        if results == '':
            results = self.results
        if self.nosub:
            print("too complicated to show the code, read the source :), sorry.")
            return None
        else:
            self._io.dataframe2sasdata(df, table, libref, keep_outer_quotes)

        if self.exist(table, libref):
            return SASdata(self, libref, table, results)
        else:
            return None