def METHOD_NAME(self, orm):
    # Changing field 'HostMaintenance.finished_at'
    db.alter_column(u'maintenance_hostmaintenance', 'finished_at', self.gf(
        'django.db.models.fields.DateTimeField')(null=True))
    # Changing field 'HostMaintenance.started_at'
    db.alter_column(u'maintenance_hostmaintenance', 'started_at', self.gf(
        'django.db.models.fields.DateTimeField')(null=True))
    # Changing field 'HostMaintenance.main_log'
    db.alter_column(u'maintenance_hostmaintenance', 'main_log', self.gf(
        'django.db.models.fields.TextField')(null=True))