Evaluate if a particular EC respect restrictions contains in a Collection
of String defining invalid EC EC hierarchy is considered during the
evaluation
GAF 2 parser used to construct a graph from a GAF 2.0 annotation file
The parser consider considering GAF 2.0 specification provided at
http://wiki.geneontology.org/index.php/GO_Consortium_web_GAF2.0_documentation
http://www.geneontology.org/GO.format.gaf-2_0.shtml
TODO - Manage multiple organism specification : taxon:1|taxon:1000