def start_session(self, b_hold_session, sig_doc_xml=None, datafile=None):
response = self.__invoke('<STR_LIT>', {<EOL>'<STR_LIT>': b_hold_session,<EOL>'<STR_LIT>': sig_doc_xml or SkipValue,<EOL>'<STR_LIT>': datafile or SkipValue,<EOL>'<STR_LIT>': SkipValue,<EOL>})<EOL>if response['<STR_LIT>']:<EOL><INDENT>self.data_files = []<EOL>self.session_code = response['<STR_LIT>']<EOL>if sig_doc_xml:<EOL><INDENT>self.container = PreviouslyCreatedContainer()<EOL><DEDENT>return True<EOL><DEDENT>return False<EOL>
Start a DigidocService session

        :return: True if session was started and session code was stored in I{session_code}