Trivial fusion category

The rank-one fusion category is the split skeletal presentation of $\operatorname{Vec}_K$, the category of finite-dimensional $K$-vector spaces from Etingof et al. (2015), Example 2.3.3, p. 26. Its only simple object is the tensor unit, and its fusion and associativity constraints are trivial.

The intended entry point is trivial_fusion_category(K), where $K$ must be a field, for the rank-one split skeletal fusion category over $K$. At present this constructor throws an error before returning a category and is therefore unavailable. The intended model has the tensor unit as its only simple object and the identity associator. Although $\operatorname{Vec}_K$ has its standard symmetric braiding, the intended code presently installs no braiding data.