docs: def dependencies(cls):
          """Returns a list of all dependent tables,
          in the order they are defined.
  
          Add new dependencies for source and every post proecssor like this::
  
              source.dependencies = [PersonalData]
              some_post_processor.dependencies = [SomeOtherTable, AnotherTable]
  
          `some_post_processor.dependencies` needs to be placed after
          `some_post_processor` is defined.
          """
          dependencies = []
          try:
              dependencies += cls.source.dependencies
          except AttributeError:
              pass
          for processor in cls.post_processors(cls):
              try:
                  assert isinstance(processor.dependencies, list), \
                      "{}.dependencies must be a list".format(processor.__name__)
                  dependencies += processor.dependencies
              except AttributeError:
                  pass
          return dependencies