new_contents: from __future__ import print_function
  
  import numpy
  
  from molml.features import CoulombMatrix
  from molml.crystal import GenerallizedCrystal, EwaldSumMatrix, SineMatrix
  
  
  # Define some base data
  H2_ELES = ['H', 'H']
  H2_NUMS = [1, 1]
  H2_COORDS = numpy.array([
      [0.0, 0.0, 0.0],
      [1.0, 0.0, 0.0],
  ])
  H2_CONNS = {
      0: {1: '1'},
      1: {0: '1'},
  }
  H2_UNIT = numpy.array([
      [2., .5, 0.],
      [.25, 1., 0.],
      [0., .3, 1.],
  ])
  
  radius = 4.1
  input_type = ("elements", "coords", "unit_cell")
  X = (H2_ELES, H2_COORDS, H2_UNIT)
  
  if __name__ == "__main__":
      trans = EwaldSumMatrix(input_type=input_type, G_max=3.2, L_max=2.1)
      res = trans.fit_transform([X])
      print(res)
  
      trans = SineMatrix(input_type=input_type)
      res = trans.fit_transform([X])
      print(res)
  
      # Example of generallized crystal
      # Any transformer can be used as it just expands the molecule using the
      # unit cell and coordinates.
      trans = GenerallizedCrystal(CoulombMatrix(input_type=input_type),
                                  radius=radius)
      res = trans.fit_transform([X])
      print(res)
  
subject: Add example script for crystals