get rid of hlist and add_centers in return

this was discussed with Leah; they actually don't need it for mixed BE

Author: mcocdawc

src/quemb/molbe/autofrag.py

@@ -337,7 +337,7 @@ def autogen(
     edgsites : list of list of list of int
         List of edge sites for each fragment where each edge is a list of LO indices.
     center : list of list of int
-        List of center indices for each edge.
+        List of the fragment index of each edge site for all fragments.
     edge_idx : list of list of list of int
         List of edge indices for each fragment where each edge index is a list of
         LO indices.
@@ -353,11 +353,6 @@ def autogen(
         Heavy atom indices for each fragment, per fragment
     cen: list
         Atom indices of all centers
-    hlist: list of lists
-        All hydrogen atom indices for each fragment, per fragment
-    add_centers: list of lists
-        "additional centers" for all fragments, per fragment: contains heavy atoms
-        which are not centers in any other fragments
     """
 
     if not valence_only:
@@ -772,6 +767,4 @@ def autogen(
         ebe_weight,
         Frag,
         cen,
-        hlist,
-        add_centers,
     )

src/quemb/molbe/fragment.py

@@ -58,7 +58,6 @@ def __init__(
         mol=None,
         frozen_core=False,
     ):
-        # Initialize class attributes
         self.mol = mol
         self.frag_type = frag_type
         self.fsites = []
@@ -73,12 +72,8 @@ def __init__(
         self.frozen_core = frozen_core
         self.iao_valence_basis = iao_valence_basis
         self.valence_only = valence_only
-
-        # Initialize class attributes necessary for mixed-basis BE
         self.Frag_atom = []
         self.center_atom = []
-        self.hlist_atom = []
-        self.add_center_atom = []
 
         # Check for frozen core approximation
         if frozen_core:
@@ -135,8 +130,6 @@ def __init__(
                 self.ebe_weight,
                 self.Frag_atom,
                 self.center_atom,
-                self.hlist_atom,
-                self.add_center_atom,
             ) = fgs
             self.Nfrag = len(self.fsites)