docs: def create_grade(self, grade_form):
          """Creates a new ``Grade``.
  
          arg:    grade_form (osid.grading.GradeForm): the form for this
                  ``Grade``
          return: (osid.grading.Grade) - the new ``Grade``
          raise:  IllegalState - ``grade_form`` already used in a create
                  transaction
          raise:  InvalidArgument - one or more of the form elements is
                  invalid
          raise:  NullArgument - ``grade_form`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          raise:  Unsupported - ``grade_form`` did not originate from
                  ``get_grade_form_for_create()``
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for
          # osid.repository.AssetAdminSession.create_asset_content_template
          from dlkit.abstract_osid.grading.objects import GradeForm as ABCGradeForm
          collection = JSONClientValidated('grading',
                                           collection='GradeSystem',
                                           runtime=self._runtime)
          if not isinstance(grade_form, ABCGradeForm):
              raise errors.InvalidArgument('argument type is not an GradeForm')
          if grade_form.is_for_update():
              raise errors.InvalidArgument('the GradeForm is for update only, not create')
          try:
              if self._forms[grade_form.get_id().get_identifier()] == CREATED:
                  raise errors.IllegalState('grade_form already used in a create transaction')
          except KeyError:
              raise errors.Unsupported('grade_form did not originate from this session')
          if not grade_form.is_valid():
              raise errors.InvalidArgument('one or more of the form elements is invalid')
          grade_form._my_map['_id'] = ObjectId()
          grade_system_id = Id(grade_form._my_map['gradeSystemId']).get_identifier()
          grade_system = collection.find_one(
              {'$and': [{'_id': ObjectId(grade_system_id)},
                        {'assigned' + self._catalog_name + 'Ids': {'$in': [str(self._catalog_id)]}}]})
          grade_system['grades'].append(grade_form._my_map)
          result = collection.save(grade_system)
  
          self._forms[grade_form.get_id().get_identifier()] = CREATED
          from .objects import Grade
          return Grade(
              osid_object_map=grade_form._my_map,
              runtime=self._runtime,
              proxy=self._proxy)