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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 centre_of_mass(self):
 """Returns the centre of mass of AMPAL object. Notes ----- All atoms are included in calculation, call `centre_of_mass` manually if another selection is require. Returns ------- centre_of_mass : numpy.array 3D coordinate for the centre of mass. """

        elts = set([x.element for x in self.get_atoms()])
        masses_dict = {e: ELEMENT_DATA[e]['atomic mass'] for e in elts}
        points = [x._vector for x in self.get_atoms()]
        masses = [masses_dict[x.element] for x in self.get_atoms()]
        return centre_of_mass(points=points, masses=masses)