code: def listPhysicsGroups(self, physics_group_name=""):
          
          if not isinstance(physics_group_name, basestring):
              dbsExceptionHandler('dbsException-invalid-input',
                  'physics group name given is not valid : %s' %
                   physics_group_name)
          else:
              try:
                  physics_group_name = str(physics_group_name)
              except:
                   dbsExceptionHandler('dbsException-invalid-input',
                                   'physics group name given is not valid : %s' %
                                    physics_group_name)
  
          conn = self.dbi.connection()
          try:
              result = self.pglist.execute(conn, physics_group_name)
              return result
          finally:
              if conn:
                  conn.close()
docs: Returns all physics groups if physics group names are not passed.