This package contains classes for working with content models. In this implementation, the standardized content model is pre-processed by `transformer` into an instance of `node`. Node holds a single element of the content model with the optional unary operation. The derived class `list` holds multiple nodes connected by the same binary operation. As the members of this `list` can also be lists itself, these structures support the most of required operations. Several cases when the model cannot be expressed using BNF syntax are handled providing specialised classes that are also derived from `node`.

@author Audrius Meskauskas, Lithuania