How to use the dagster.solid function in dagster

@solid
def cache_file_from_s3(context, s3_coord: S3Coordinate) -> str:
    # we default the target_key to the last component of the s3 key.
    target_key = s3_coord['key'].split('/')[-1]

    with get_temp_file_name() as tmp_file:
        boto3.client('s3').download_file(
            Bucket=s3_coord['bucket'], Key=s3_coord['key'], Filename=tmp_file
        )

        file_cache = context.resources.file_cache
        with open(tmp_file, 'rb') as tmp_file_object:
            # returns a handle rather than a path
            file_handle = file_cache.write_file_object(target_key, tmp_file_object)
            return file_handle.path

@solid(config_field=Field(Int))
def add_n(context, x: Int) -> int:
    return x + context.solid_config

    @solid(config=Field(String))
    def configured(context):
        called['configured'] = True
        assert context.solid_config == 'yes'

    @solid(outputs=[OutputDefinition(types.String)])
    def str_as_output(_info):
        return 'bar'

    @solid(config={'inner': Field(String)})
    def inner_solid(context):
        return context.solid_config['inner']

    @solid(output_defs=[])
    def success_expectation_solid(_context):
        yield ExpectationResult(success=True, description='This is always true.')

    @solid
    def check_context_stack(info):
        assert info.context.get_context_value('foo') == 'bar'
        assert info.context.get_context_value('quux') == 'baaz'
        called['yup'] = True

@solid(
    input_defs=[
        InputDefinition('in_1', Int),
        InputDefinition('in_2', Int),
        InputDefinition('in_3', Int),
        InputDefinition('in_4', Int),
    ],
    output_defs=[OutputDefinition(Int)],
)
def total(_, in_1, in_2, in_3, in_4):
    return in_1 + in_2 + in_3 + in_4

@solid(required_resource_keys={'volume'})
def unzip_files(context, file_names: List[str], source_dir: str, target_dir: str) -> List[str]:
    # mount dirs onto volume
    zipfile_location = os.path.join(context.resources.volume, source_dir)
    csv_location = os.path.join(context.resources.volume, target_dir)
    if not os.path.exists(csv_location):
        os.mkdir(csv_location)
    return [
        _unzip_file(os.path.join(zipfile_location, file_name), csv_location)
        for file_name in file_names
    ]

@solid(
    name='download_from_s3_to_file',
    config={
        'bucket': Field(String, description='S3 bucket name'),
        'key': Field(String, description='S3 key name'),
        'target_folder': Field(
            Path, description=('Specifies the path at which to download the object.')
        ),
        'skip_if_present': Field(Bool, is_optional=True, default_value=False),
    },
    description='Downloads an object from S3 to a file.',
    output_defs=[
        OutputDefinition(FileExistsAtPath, description='The path to the downloaded object.')
    ],
    required_resource_keys={'s3'},
)
def download_from_s3_to_file(context):