add checks for DAG where relevant in GraphicalModels

globalMarkov add check for DAG
•   !pairMarkov - Graph or Digraph (checks for DAG)
•   l!ocalMarkov - Graph or Digraph (checks for DAG)
•   !globalMarkov - Graph or Digraph (does not check for DAG)
•   !markovRing - Sequence
•   !gaussianRing- ZZ or Graph or Digraph or MixedGraph (doesn’t check for DAG)
•   !markovMatrices - (Ring,List,List) or (Ring, List) check that it is a Markov ring
•   !covarianceMatrix - Ring, checks that is a Gaussian Ring
•   conditionalIndependenceIdeal - (Ring, List) or (Ring, List, List), checks whether ring is Gaussian or Markov. In the case of (Ring, List, List), only takes Markov rings
•   gaussianParametrization- Ring, checks that is Gaussian ring of MixedGraph without undirected edges
•   gaussianVanishingIdeal - Ring, checks that this is a Gaussian ring go Graph or Digraph or MixedGraph without undirected part
•   !discreteVanishingIdeal - (Ring, Digraph), checks that ring is Markov and the number of vertices is compatible but not that the graph is a Digraph
•   trekSeparation - MixedGraph, checks that there are no undirected edges but does not check that this is a MixedGraph or that both Digraph and Bigraph are present
•   trekIdeal - (Ring,G), where G can be Graph, Digraph or MixedGraph with directed and bidirected edges. Does not check that G has correct type but checks compatibility of variable names in the Ring and G
•   marginMap - (ZZ,Ring), checks that ZZ is compatible with the Ring and that Ring is a MarkovRing
•   inverseMarginMap- (ZZ,Ring), checks that ZZ is compatible with the Ring and that Ring is a MarkovRing
•   hiddenMap - (ZZ,Ring), checks that ZZ is compatible with the Ring and that Ring is a MarkovRing
•   identifyParameters
Macaulay2 / Workshop-2020-Warwick

add checks for DAG where relevant in GraphicalModels #204
