Removed completed TODOs.

DG_Approximation.py

@@ -7,11 +7,8 @@ TODO: Contemplate saving 5-CV split and evaluating models separately
 TODO: Contemplate separating cell average and reconstruction calculations
     completely
 TODO: Contemplate removing Methods section from class docstring
-TODO: Contemplate moving stiffness and boundary matrix from update scheme
-    to basis
 
 Urgent:
-TODO: Improve docstring for Basis class
 TODO: Enforce abstract classes/methods (abc.ABC, abc.abstractmethod)
 TODO: Introduce Mesh class
     (mesh, cell_len, num_grid_cells, bounds, num_ghost_cells, etc.)
@@ -26,6 +23,7 @@ TODO: Combine ANN workflows
 TODO: Add an environment file for Snakemake
 
 Critical, but not urgent:
+TODO: Check sign change in stiffness matrix to accommodate negative wave speed
 TODO: Investigate g-mesh(?)
 TODO: Force input_size for each ANN model to be stencil length
 TODO: Use full path for ANN model state