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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_layout(self, size = None):
 """utility function to create layout with the default font. Size and alignment parameters are shortcuts to according functions of the pango.Layout"""

        if not self.context:
            # TODO - this is rather sloppy as far as exception goes
            #        should explain better
            raise Exception("Can not create layout without existing context!")

        layout = pangocairo.create_layout(self.context)
        font_desc = pango.FontDescription(_font_desc)
        if size: font_desc.set_absolute_size(size * pango.SCALE)

        layout.set_font_description(font_desc)
        return layout