Make code PEP8 compliant

[mathurinm]

HI @resfahani

checking for PEP8 errors with flake8 results in a few errors:

./SRC/sparseTF.py:18:80: E501 line too long (92 > 79 characters)
./SRC/sparseTF.py:22:25: W291 trailing whitespace
./SRC/sparseTF.py:33:1: E303 too many blank lines (3)
./SRC/sparseTF.py:33:43: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:33:45: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:33:58: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:33:60: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:37:1: W293 blank line contains whitespace
./SRC/sparseTF.py:41:5: E731 do not assign a lambda expression, use a def
./SRC/sparseTF.py:41:17: E203 whitespace before ':'
./SRC/sparseTF.py:41:55: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:41:57: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:41:69: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:41:71: E251 unexpected spaces around keyword / parameter equals
./SRC/sparseTF.py:41:80: E501 line too long (100 > 79 characters)
./SRC/sparseTF.py:42:1: W293 blank line contains whitespace
./SRC/sparseTF.py:43:1: W293 blank line contains whitespace
./SRC/sparseTF.py:44:5: E303 too many blank lines (2)
./SRC/sparseTF.py:48:1: W293 blank line contains whitespace
./SRC/sparseTF.py:49:1: E265 block comment should start with '# '
etc.

you could fix them easily by using an automatic linter in your text editor

Best,
Mathurin