old_contents: class Experiment:
      """
      Base class for all experiments.
  
      """
  
new_contents: """
  The collection of classes to describe experiments for CA models.
  
  Experiment is a class with CA parameters stored as class
  variables. Different models may have a different set of parameters. To
  make sure all set correct, you should inherit your experiments from
  :class:`Experiment` class.
  
  The quick example::
  
      from xentica import core, seeds
  
      class MyExperiment(core.Experiment):
          # RNG seed string
          word = "My Special String"
          # field size
          size = (640, 360, )
          # initial field zoom
          zoom = 3
          # initial field shift
          pos = [0, 0]
          # A pattern used in initial board state generation.
          # BigBang is a small area initialized with high-density random values.
          seed = seeds.patterns.BigBang(
              # position Big Bang area
              pos=(320, 180),
              # size of Big Bang area
              size=(100, 100),
              # algorithm to generate random values
              vals={
                  "state": seeds.random.RandInt(0, 1),
              }
         )
  
  
  
  """
  
  
  class Experiment:
      """
      Base class for all experiments.
  
      Right now doing nothing, but will be improved in future
      versions. So it is adviced to inherit your experiments from it.
  
      """
  
subject: Add docstrings to core.experiment module (#23, #27)