def check_symbol(self, symbol, s_list=None):
        
        all_symbols = list()
        
        # Create a super-set of symbols.
        if s_list is not None:
            all_symbols = self.get_symbols_from_list(s_list)
        else:
            all_symbols = self.get_all_symbols()
        
        # Check if the symbols is present.
        if ( symbol in all_symbols ):
            return True
        else:
            return False
Returns a validator for v1 service request/response protos.
dataset/ETHPy150Open QuantSoftware/QuantSoftwareToolkit/QSTK/qstkutil/DataAccess.py/DataAccess.check_symbol--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/python-compat-runtime/appengine-compat/exported_appengine_sdk/google/appengine/datastore/cloud_datastore_validator.py/get_service_validator