Add tests for flattened edge weight. Update for belief.
Add tests for flattened edge weight. Update for belief.

sorgerlab/indra,johnbachman/indra,johnbachman/indra,sorgerlab/belpy,sorgerlab/indra,bgyori/indra,sorgerlab/indra,johnbachman/indra,johnbachman/belpy,bgyori/indra,sorgerlab/belpy,bgyori/indra,johnbachman/belpy,sorgerlab/belpy,johnbachman/belpy