Computes the k-skeleton of the mapper by computing the nerve of the pullback of `cover`

member.

k | the maximal dimension to consider. |
---|

The primary output of the Mapper method is a simplicial complex. With `MapperRef`

objects,
the simplicial complex is stored as a `simplextree`

. The underlying complex does not need to be modified by the user, i.e. is completely maintained by `MapperRef`

methods
(e.g. this method, `construct_nerve`

, etc.).

This function computes the k-skeleton inductively, e.g. by first computing the vertices,
then the edges, etc. up to the dimension specified. A check is performed to ensure the pullback has been decomposed, and
if not, then `construct_pullback`

is called.

For an algorithmic description of this process, see Singh et. al, section 3.2.

Gurjeet Singh, Facundo Mémoli, and Gunnar Carlsson. "Topological methods for the analysis of high dimensional data sets and 3d object recognition." SPBG. 2007.