Fix 3 pre-existing notebook logic bugs

- search.ipynb: cell 112 redefines hill_climbing as a TSP-specific version
  (using two_opt), shadowing the library's generic one; the later Peak-Finding
  section then called it on a PeakFindingProblem (no two_opt) and failed.
  Re-import the library hill_climbing right before that section.
- chapter22/Parsing.ipynb: CYK_parse returns a probability table
  (defaultdict(float)), but the cells called .leaves on the float values.
  Display the probabilities instead (full table; VP entries).
- chapter19/Optimizer and Backpropagation.ipynb: pseudocode() is a string API
  (e.g. pseudocode('Back-Prop-Learning')); pseudocode(adam) passed a function
  and Adam has no aima-pseudocode entry. Dropped it; psource(adam) still shows
  the implementation.

All three now run clean headless; no module changes (test suite unaffected).

Author: dmeoli

notebooks/chapter19/Optimizer and Backpropagation.ipynb

@@ -222,7 +222,6 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "pseudocode(adam)\n",
     "psource(adam)"
    ]
   },

notebooks/chapter22/Parsing.ipynb

@@ -302,7 +302,7 @@
     }
    ],
    "source": [
-    "parses = {k: p.leaves for k, p in P.items()}\n",
+    "parses = {k: p for k, p in P.items() if p}\n",
     "\n",
     "print(parses)"
    ]
@@ -329,8 +329,9 @@
     }
    ],
    "source": [
-    "for subtree in P['VP', 2, 3].leaves:\n",
-    "    print(subtree.leaves)"
+    "# CYK_parse returns a probability table P[(symbol, start, length)] -> probability;\n",
+    "# show where the grammar can parse a VP (verb phrase) and with what probability\n",
+    "print({k: p for k, p in P.items() if k[0] == 'VP' and p})"
    ]
   },
   {

notebooks/search.ipynb

@@ -3479,6 +3479,16 @@
     "This could also be solved by Hill Climbing as follows."
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# re-import the library's generic hill_climbing (the TSP cell above shadowed it with a two_opt-based version)\n",
+    "from aima.search import hill_climbing"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 15,