def sasdata(self, table: str, libref: str = '', results: str = '', dsopts: dict = None) -> 'SASdata':
        """
        Method to define an existing SAS dataset so that it can be accessed via SASPy

        :param table:   the name of the SAS Data Set
        :param libref:  the libref for the Data Set, defaults to WORK, or USER if assigned
        :param results: format of results, SASsession.results is default, Pandas, HTML and TEXT are the valid options
        :param dsopts: a dictionary containing any of the following SAS data set options(where, drop, keep, obs, firstobs):

            - where is a string
            - keep are strings or list of strings.
            - drop are strings or list of strings.
            - obs is a numbers - either string or int
            - first obs is a numbers - either string or int
            - format is a string or dictionary { var: format }

            .. code-block:: python

                             {'where'    : 'msrp < 20000 and make = "Ford"'
                              'keep'     : 'msrp enginesize Cylinders Horsepower Weight'
                              'drop'     : ['msrp', 'enginesize', 'Cylinders', 'Horsepower', 'Weight']
                              'obs'      :  10
                              'firstobs' : '12'
                              'format'  : {'money': 'dollar10', 'time': 'tod5.'}
                             }

        :return: SASdata object
        """
        dsopts = dsopts if dsopts is not None else {}

        if results == '':
            results = self.results
        sd = SASdata(self, libref, table, results, dsopts)
        if not self.exist(sd.table, sd.libref):
            if not self.batch:
                print(
                    "Table " + sd.libref + '.' + sd.table + " does not exist. This SASdata object will not be useful until the data set is created.")
        return sd