message: Updated MBTR docstring.
diff: @@ -20,15 +20,15 @@ class MBTR(Descriptor):
  This implementation provides the following geometry functions:
  - -k=1: atomic number
  - -k=2: inverse distances
  - -k=3: cosines of angles
  + * k=1: atomic number
  + * k=2: inverse distances
  + * k=3: cosines of angles
  and the following weighting functions:
  - -k=1: unity(=no weighting)
  - -k=2: unity(=no weighting), exponential (:math:`e^-(sx)`)
  - -k=3: unity(=no weighting), exponential (:math:`e^-(sx)`)
  + * k=1: unity(=no weighting)
  + * k=2: unity(=no weighting), exponential (:math:`e^-(sx)`)
  + * k=3: unity(=no weighting), exponential (:math:`e^-(sx)`)
  You can use this descriptor for finite and periodic systems. When dealing
  with periodic systems, it is advisable to use a primitive cell, or if
  