def linear_kernel(X, Y=None):
 (X, Y) = check_pairwise_arrays(X, Y)
 return safe_sparse_dot(X, Y.T, dense_output=True)

def linear_kernel ( X , Y = None ) : ( X , Y ) = check_pairwise_arrays ( X , Y ) return safe_sparse_dot ( X , Y . T , dense_output = True )
compute the linear kernel between x and y .