code: def visitParam_def(self, ctx:SystemRDLParser.Param_defContext):
          
          self.compiler.namespace.enter_scope()
  
          param_defs = []
          for elem in ctx.getTypedRuleContexts(SystemRDLParser.Param_def_elemContext):
              param_def = self.visit(elem)
              param_defs.append(param_def)
  
          self.compiler.namespace.exit_scope()
          return param_defs
docs: Parameter Definition block