initializing graph files
adding no nodes test
no nodes passes
Node test passed
no edges test passed
edges test passed
add node test added
add new node test passes
added test add edge
add edge test passed
test to see if new nodes are in list
add missing nodes when adding edge
add del node test
delete node if exists test works
remove node that does not exist raises error
test to delete edges with nodes passes
adding delete edge test
remove edge works
add raise error test
error raised if edge not in graph