sagemathgh-36170: Fix the ascii art for the Heisenberg Lie algebras

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Applying `ascii_art(x)` to any element of the finite-dimensional
Heisenberg algebra raises an error due to a missing method
`_ascii_art_term`. We implement this.

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URL: sagemath#36170
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton

build/pkgs/configure/checksums.ini

@@ -1,4 +1,4 @@
 tarball=configure-VERSION.tar.gz
-sha1=80ee52a3b6855149693204f0816bd0690947e7ae
-md5=4292c175bba9299bd057980cec7060fd
-cksum=3914108326
+sha1=402380b47b913708343c09557a28a1a7b43d836b
+md5=97856a160839007d3a546bfedb7f47b0
+cksum=1229430481

build/pkgs/configure/package-version.txt

@@ -1 +1 @@
-57852a89c5c274ec6dbdd9269042972c7343e3ec
+e091f3a0d28dd7daf0b1fade564aac5fe5006feb

src/sage/algebras/lie_algebras/heisenberg.py

@@ -122,6 +122,23 @@ def _repr_term(self, m):
         """
         return m
 
+    def _ascii_art_term(self, m):
+        r"""
+        Return a string representation of the term indexed by ``m``.
+
+        EXAMPLES::
+
+            sage: H = lie_algebras.Heisenberg(QQ, 3)
+            sage: H._ascii_art_term('p1')
+            p1
+            sage: H._ascii_art_term('z')
+            z
+            sage: ascii_art(sum(i * b for i, b in enumerate(H.basis())))
+            p2 + 2*p3 + 3*q1 + 4*q2 + 5*q3 + 6*z
+        """
+        from sage.typeset.ascii_art import ascii_art
+        return ascii_art(m)
+
     def _latex_term(self, m):
         r"""
         Return a string representation of the term indexed by ``m``.