How to call the load data function

Note: the function returns two (!) values;
a dictionary of lists, plus a float

It is common that output data from a Python function are returned, and multiple data structures can be returned (actually packed as a tuple, a kind of ``constant list'')

Here is how the function is called:

y, dt = load_data('somedatafile.dat')
print y

Output from print y:

>>> y
{'tmp-model2': [1.0, 0.188, 0.25], 
'tmp-model1': [0.10000000000000001, 0.10000000000000001, 
 0.20000000000000001], 
'tmp-measurements': [0.0, 0.10000000000000001, 
 0.20000000000000001]}