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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update_gradebook_column(self, gradebook_column_form):
 """Updates an existing gradebook column. arg: gradebook_column_form (osid.grading.GradebookColumnForm):
 the form containing the elements to be updated raise: IllegalState - ``gradebook_column_form`` already used in an update transaction raise: InvalidArgument - the form contains an invalid value raise: NullArgument - ``gradebook_column_form`` is ``null`` raise: OperationFailed - unable to complete request raise: PermissionDenied - authorization failure raise: Unsupported - ``gradebook_column_form`` did not originate from ``get_gradebook_column_form_for_update()`` *compliance: mandatory -- This method must be implemented.* """

        collection = JSONClientValidated('grading',
                                         collection='GradebookColumn',
                                         runtime=self._runtime)
        if not isinstance(gradebook_column_form, ABCGradebookColumnForm):
            raise errors.InvalidArgument('argument type is not an GradebookColumnForm')
        if not gradebook_column_form.is_for_update():
            raise errors.InvalidArgument('the GradebookColumnForm is for update only, not create')
        try:
            if self._forms[gradebook_column_form.get_id().get_identifier()] == UPDATED:
                raise errors.IllegalState('gradebook_column_form already used in an update transaction')
        except KeyError:
            raise errors.Unsupported('gradebook_column_form did not originate from this session')
        if not gradebook_column_form.is_valid():
            raise errors.InvalidArgument('one or more of the form elements is invalid')

        # check that there are no entries, if updating the gradeSystemId
        old_column = collection.find_one({"_id": gradebook_column_form._my_map['_id']})
        if old_column['gradeSystemId'] != gradebook_column_form._my_map['gradeSystemId']:
            if self._has_entries(gradebook_column_form.id_):
                raise errors.IllegalState('Entries exist in this gradebook column. ' +
                                          'Cannot change the grade system.')

        collection.save(gradebook_column_form._my_map)

        self._forms[gradebook_column_form.get_id().get_identifier()] = UPDATED

        # Note: this is out of spec. The OSIDs don't require an object to be returned:
        return objects.GradebookColumn(
            osid_object_map=gradebook_column_form._my_map,
            runtime=self._runtime,
            proxy=self._proxy)