How to use the igraph.drawing.utils.BoundingBox function in igraph

def fit_into(self, bbox, keep_aspect_ratio=True):
        """Fits the layout into the given bounding box.

        The layout will be modified in-place.

        @param bbox: the bounding box in which to fit the layout. If the
          dimension of the layout is d, it can either be a d-tuple (defining
          the sizes of the box), a 2d-tuple (defining the coordinates of the
          top left and the bottom right point of the box), or a L{BoundingBox}
          object (for 2D layouts only).
        @param keep_aspect_ratio: whether to keep the aspect ratio of the current
          layout. If C{False}, the layout will be rescaled to fit exactly into
          the bounding box. If C{True}, the original aspect ratio of the layout
          will be kept and it will be centered within the bounding box.
        """
        if isinstance(bbox, BoundingBox):
            if self._dim != 2:
                raise TypeError("bounding boxes work for 2D layouts only")
            corner, target_sizes = [bbox.left, bbox.top], [bbox.width, bbox.height]
        elif len(bbox) == self._dim:
            corner, target_sizes = [0.] * self._dim, list(bbox)
        elif len(bbox) == 2 * self._dim:
            corner, opposite_corner = list(bbox[0:self._dim]), list(bbox[self._dim:])
            for i in xrange(self._dim):
                if corner[i] > opposite_corner[i]:
                    corner[i], opposite_corner[i] = opposite_corner[i], corner[i]
            target_sizes = [max_val-min_val \
                    for min_val, max_val in izip(corner, opposite_corner)]

        try:
            mins, maxs = self.boundaries()
        except ValueError:

The bounding box of the layout is the smallest box enclosing all the
        points in the layout.

        @param border: this value gets subtracted from the minimum bounds
          and gets added to the maximum bounds before returning the coordinates
          of the box. Defaults to zero.
        @return: the coordinates of the lower left and the upper right corner
          of the box. "Lower left" means the minimum coordinates and "upper right"
          means the maximum. These are encapsulated in a L{BoundingBox} object.
        """
        if self._dim != 2:
            raise ValueError("Layout.boundary_box() supports 2D layouts only")

        try:
            (x0, y0), (x1, y1) = self.boundaries(border)
            return BoundingBox(x0, y0, x1, y1)
        except ValueError:
            return BoundingBox(0, 0, 0, 0)

def bounding_box(self):
        """Returns the bounding box of the Cairo surface as a
        L{BoundingBox} object"""
        return BoundingBox(self.bbox)

def bbox(self, bbox):
        """Sets the bounding box of the drawing area where this drawer
        will draw."""
        if not isinstance(bbox, BoundingBox):
            self._bbox = BoundingBox(bbox)
        else:
            self._bbox = bbox

def bbox(self, bbox):
        """Sets the bounding box of the drawing area where this drawer
        will draw."""
        if not isinstance(bbox, BoundingBox):
            self._bbox = BoundingBox(bbox)
        else:
            self._bbox = bbox

        @param border: this value gets subtracted from the minimum bounds
          and gets added to the maximum bounds before returning the coordinates
          of the box. Defaults to zero.
        @return: the coordinates of the lower left and the upper right corner
          of the box. "Lower left" means the minimum coordinates and "upper right"
          means the maximum. These are encapsulated in a L{BoundingBox} object.
        """
        if self._dim != 2:
            raise ValueError("Layout.boundary_box() supports 2D layouts only")

        try:
            (x0, y0), (x1, y1) = self.boundaries(border)
            return BoundingBox(x0, y0, x1, y1)
        except ValueError:
            return BoundingBox(0, 0, 0, 0)

    @bbox.setter
    def bbox(self, bbox):
        """Sets the bounding box of the drawing area where this drawer
        will draw."""
        if not isinstance(bbox, BoundingBox):
            self._bbox = BoundingBox(bbox)
        else:
            self._bbox = bbox

        @param border: this value gets subtracted from the minimum bounds
          and gets added to the maximum bounds before returning the coordinates
          of the box. Defaults to zero.
        @return: the coordinates of the lower left and the upper right corner
          of the box. "Lower left" means the minimum coordinates and "upper right"
          means the maximum. These are encapsulated in a L{BoundingBox} object.
        """
        if self._dim != 2:
            raise ValueError("Layout.boundary_box() supports 2D layouts only")

        try:
            (x0, y0), (x1, y1) = self.boundaries(border)
            return BoundingBox(x0, y0, x1, y1)
        except ValueError:
            return BoundingBox(0, 0, 0, 0)

def fit_into(self, bbox, keep_aspect_ratio=True):
        """Fits the layout into the given bounding box.

        The layout will be modified in-place.

        @param bbox: the bounding box in which to fit the layout. If the
          dimension of the layout is d, it can either be a d-tuple (defining
          the sizes of the box), a 2d-tuple (defining the coordinates of the
          top left and the bottom right point of the box), or a L{BoundingBox}
          object (for 2D layouts only).
        @param keep_aspect_ratio: whether to keep the aspect ratio of the current
          layout. If C{False}, the layout will be rescaled to fit exactly into
          the bounding box. If C{True}, the original aspect ratio of the layout
          will be kept and it will be centered within the bounding box.
        """
        if isinstance(bbox, BoundingBox):
            if self._dim != 2:
                raise TypeError("bounding boxes work for 2D layouts only")
            corner, target_sizes = [bbox.left, bbox.top], [bbox.width, bbox.height]
        elif len(bbox) == self._dim:
            corner, target_sizes = [0.] * self._dim, list(bbox)
        elif len(bbox) == 2 * self._dim:
            corner, opposite_corner = list(bbox[0:self._dim]), list(bbox[self._dim:])
            for i in xrange(self._dim):
                if corner[i] > opposite_corner[i]:
                    corner[i], opposite_corner[i] = opposite_corner[i], corner[i]
            target_sizes = [max_val-min_val \
                    for min_val, max_val in izip(corner, opposite_corner)]

        try:
            mins, maxs = self.boundaries()
        except ValueError: