code: def setup_random_structure(self, coordination):
          
          aa = 0.4
          bb = -0.2
          coords = list()
          for ii in range(coordination + 1):
              coords.append(aa * np.random.random_sample(3, ) + bb)
          self.set_structure(
              lattice=np.array([[10, 0, 0], [0, 10, 0], [0, 0, 10]], np.float),
              species=["Si"] * (coordination + 1),
              coords=coords,
              coords_are_cartesian=False)
          self.setup_random_indices_local_geometry(coordination)
docs: Sets up a purely random structure with a given coordination.
          :param coordination: coordination number for the random structure