Make flake8 linting

Add gitignore

tests/test_graph_laplacian.py

@@ -2,14 +2,15 @@ import unittest
 import numpy as np
 import torch
 from scipy.sparse import lil_matrix, csr_matrix, coo_matrix
-
-
 import os
 import sys
 maindir = os.getcwd()
 main_path = maindir[:maindir.find('ds4ms/code')]
 sys.path.append(main_path+"/ds4ms/code/src")
-from graph_laplacian import create_laplacian_matrix, delete_from_csr, remove_vertex, laplacian, unnormalized_laplacian, laplacian_chain, unnormalized_laplacian_chain
+from graph_laplacian import create_laplacian_matrix, delete_from_csr, \
+    remove_vertex, laplacian, unnormalized_laplacian, laplacian_chain, \
+    unnormalized_laplacian_chain
+
 
 class TestGraphLaplacian(unittest.TestCase):
 
@@ -66,5 +67,6 @@ class TestGraphLaplacian(unittest.TestCase):
         self.assertEqual(L.shape, (nx, nx))
         self.assertIsInstance(L, csr_matrix)
 
+
 if __name__ == '__main__':
-    unittest.main()
+    unittest.main()