The evalution of observables of iPEPS is realized through reduced density matrices. In order to construct them, one first computes an effective environment consisting of a set of tensors that approximate contraction of (infinite) parts of the tensor network. Once done, these environment tensors can be combined with on-site tensors to build various reduced density matrices. Following modules encapsulate CTMRG algorithm which computes the environment tensors for various iPEPS. Once done, the convenience functions facilitate construction of reduced density matrices of commonly used regions and computation correlations functions.