def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def __init__(self, root, split="train", pass_name="clean", transforms=None):
        super().__init__(root=root, transforms=transforms)

        verify_str_arg(split, "split", valid_values=("train", "test"))
        verify_str_arg(pass_name, "pass_name", valid_values=("clean", "final", "both"))
        passes = ["clean", "final"] if pass_name == "both" else [pass_name]

        root = Path(root) / "Sintel"
        flow_root = root / "training" / "flow"

        for pass_name in passes:
            split_dir = "training" if split == "train" else split
            image_root = root / split_dir / pass_name
            for scene in os.listdir(image_root):
                image_list = sorted(glob(str(image_root / scene / "*.png")))
                for i in range(len(image_list) - 1):
                    self._image_list += [[image_list[i], image_list[i + 1]]]

                if split == "train":
                    self._flow_list += sorted(glob(str(flow_root / scene / "*.flo")))