Returns list of variables of the network

        Example
        -------------
        >>> from pgmpy.readwrite import BIFReader
        >>> reader = BIFReader("bif_test.bif")
        >>> reader.get_variables()
        ['light-on','bowel_problem','dog-out','hear-bark','family-out']

def get_variables(self):
        """
        Returns list of variables of the network

        Example
        -------------
        >>> from pgmpy.readwrite import BIFReader
        >>> reader = BIFReader("bif_test.bif")
        >>> reader.get_variables()
        ['light-on','bowel_problem','dog-out','hear-bark','family-out']
        """
        variable_names = []
        for block in self.variable_block():
            name = self.name_expr.searchString(block)[0][0]
            variable_names.append(name)

        return variable_names