def load_pyproject_toml(self):
        # type: () -> None
        """Load the pyproject.toml file.

        After calling this routine, all of the attributes related to PEP 517
        processing for this requirement have been set. In particular, the
        use_pep517 attribute can be used to determine whether we should
        follow the PEP 517 or legacy (setup.py) code path.
        """
        pyproject_toml_data = load_pyproject_toml(
            self.use_pep517,
            self.pyproject_toml_path,
            self.setup_py_path,
            str(self)
        )

        if pyproject_toml_data is None:
            self.use_pep517 = False
            return

        self.use_pep517 = True
        requires, backend, check, backend_path = pyproject_toml_data
        self.requirements_to_check = check
        self.pyproject_requires = requires
        self.pep517_backend = Pep517HookCaller(
            self.unpacked_source_directory, backend, backend_path=backend_path,
        )
Load the pyproject.toml file.

        After calling this routine, all of the attributes related to PEP 517
        processing for this requirement have been set. In particular, the
        use_pep517 attribute can be used to determine whether we should
        follow the PEP 517 or legacy (setup.py) code path.
        
product/gradle-plugin/src/main/python/pip/_internal/req/req_install.py