Loads a data file and sets it to self.data.

            Arguments:
            data_file -- The filename to load.

def load(self, data_file = None):
        """ Loads a data file and sets it to self.data.

            Arguments:
            data_file -- The filename to load.
        """

        if not data_file:
            data_file = ''
        elif data_file[-1] != '/':
            data_file += '/'

        if data_file[-6:] != self.lazy_folder:
            data_file += self.lazy_folder
        
        data_file += self.data_filename

        self.data = self._load(data_file)
        return self