Exports this object into a LEMS XML object

def toxml(self):
        """
        Exports this object into a LEMS XML object
        """

        return '<DerivedVariable name="{0}"'.format(self.name) +\
          (' dimension="{0}"'.format(self.dimension) if self.dimension else '') +\
          (' exposure="{0}"'.format(self.exposure) if self.exposure else '') +\
          (' select="{0}"'.format(self.select) if self.select else '') +\
          (' value="{0}"'.format(self.value) if self.value else '') +\
          (' reduce="{0}"'.format(self.reduce) if self.reduce else '') +\
          (' required="{0}"'.format(self.required) if self.required else '') +\
          '/>'