<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def load_local_dataset(self, ds_str):
        '''
        Returns a dataset instance for the local resource

        :param ds_str: Path to the resource
        '''
        if cdl.is_cdl(ds_str):
            ds_str = self.generate_dataset(ds_str)

        if netcdf.is_netcdf(ds_str):
            return MemoizedDataset(ds_str)

        # Assume this is just a Generic File if it exists
        if os.path.isfile(ds_str):
            return GenericFile(ds_str)

        raise ValueError("File is an unknown format")