docs: def _get_previous_assessment_section(self, assessment_section_id):
          """Gets the previous section before section_id.
  
          Assumes that section list exists in taken and section_id is in section list.
          Assumes that Section parts only exist as children of Assessments
  
          """
          if self._my_map['sections'][0] == str(assessment_section_id):
              raise errors.IllegalState('already at the first section')
          else:
              return self._get_assessment_section(
                  Id(self._my_map['sections'][self._my_map['sections'].index(str(assessment_section_id)) - 1]))