Function build_from_docker 

pub fn build_from_docker(
    docker_uri: &str,
    docker_dir: &Option<String>,
    output_path: &str,
    signing_certificate: &Option<String>,
    private_key: &Option<String>,
    img_name: &Option<String>,
    img_version: &Option<String>,
    metadata_path: &Option<String>,
) -> NitroCliResult<(File, BTreeMap<String, String>)>

Build an enclave image file from a Docker image.