Fix tgf output

[aeijdenberg]

Using --tgf output format seems to break on trivial examples.

e.g.

a.py:

import b
b.c()

b.py:

def c():
    pass

Results in:

$ ./pyan.py a.py b.py --tgf
Traceback (most recent call last):
  File "./pyan.py", line 849, in <module>
    main()
  File "./pyan.py", line 845, in main
    draw_uses=options.draw_uses)
  File "./pyan.py", line 734, in to_tgf
    i1 = id_map[n]
KeyError: <Node a>

By removing the if n.defined: check on line 713, this succeeds.

(The rest of this diff is just trailing whitespace removal noise)

[Technologicat]

(Now going through the PRs from here for inclusion into the Python 3 fork.)

The problem was that the defined checks were not consistent. The code creating id_map checked n.defined, whereas the code writing the edges didn't. Thus, it was trying to add edges between nodes that didn't have an ID for the .tgf, and crashed.

I solved this the other way, adding a check for n.defined in the code writing the edges. Visualizing only defined nodes and edges between them (like the GraphViz output does) should produce a cleaner graph in case of more complex input files.

On my part, thanks for the report and the test case :)

[aeijdenberg]

Thanks for the follow-up @Technologicat - I'd forgotten all about this! Glad you've found a fix, please feel free to close this PR out.

[davidfraser]

Closing as requested