update session with extracted variables mapping.
            these variables are valid in the whole running session.

def update_session_variables(self, variables_mapping):
        """ update session with extracted variables mapping.
            these variables are valid in the whole running session.
        """
        variables_mapping = utils.ensure_mapping_format(variables_mapping)
        self.session_variables_mapping.update(variables_mapping)
        self.test_variables_mapping.update(self.session_variables_mapping)