How to use the pipdeptree.Package function in pipdeptree

This association is necessary for displaying the tree in
        reverse.

        :param ReqPackage req: the requirement to associate with
        :returns: DistPackage instance

        """
        return self.__class__(self._obj, req)

    def as_dict(self):
        return {'key': self.key,
                'package_name': self.project_name,
                'installed_version': self.version}


class ReqPackage(Package):
    """Wrapper class for Requirements instance

      :param obj: The `Requirements` instance to wrap over
      :param dist: optional `pkg_resources.Distribution` instance for
                   this requirement
    """

    UNKNOWN_VERSION = '?'

    def __init__(self, obj, dist=None):
        super(ReqPackage, self).__init__(obj)
        self.dist = dist

    @property
    def version_spec(self):
        specs = sorted(self._obj.specs, reverse=True)  # `reverse` makes '>' prior to '<'

else:
            return self.render_as_branch(frozen)

    @staticmethod
    def frozen_repr(obj):
        fr = frozen_req_from_dist(obj)
        return str(fr).strip()

    def __getattr__(self, key):
        return getattr(self._obj, key)

    def __repr__(self):
        return '<{0}("{1}")>'.format(self.__class__.__name__, self.key)


class DistPackage(Package):
    """Wrapper class for pkg_resources.Distribution instances

      :param obj: pkg_resources.Distribution to wrap over
      :param req: optional ReqPackage object to associate this
                  DistPackage with. This is useful for displaying the
                  tree in reverse
    """

    def __init__(self, obj, req=None):
        super(DistPackage, self).__init__(obj)
        self.version_spec = None
        self.req = req

    def render_as_root(self, frozen):
        if not frozen:
            return '{0}=={1}'.format(self.project_name, self.version)