def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def __setattr__(self, name: str, value: Any):
        """Custom __setattr__ to allow access to metrics schema fields."""

        if not self._initialized:
            object.__setattr__(self, name, value)
            return

        if name not in self._metric_fields:
            raise RuntimeError(
                'Field: {} not defined in metirc schema'.format(name))

        self._values[name] = value