Those are the dependencies, at least. Did you try the following?
pip install pyvizgraph
Or if pip is not installed:
You might need to be root for these to install correctly.
To answer your specific question, you could enter the python interpreter and then try loading the module. If the module doesn't load, it isn't installed. To do it on a single line from the command line, try:
python -c 'import pyvizgraph'
Since it isn't installed on my system, I get the following message:
jrhorn424@hook:~ 2011-10-19 09:00:03
>> python -c 'import pyvizgraph'
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: No module named pythongraphviz