refactor(analysis): remove substitute_unbound() since it is used at…

… a single place

ibis/expr/analysis.py

@@ -173,13 +173,6 @@ def fn(node):
     return substitute(fn, node)
 
 
-def substitute_unbound(node):
-    """Rewrite `node` by replacing table expressions with an equivalent unbound table."""
-    return node.replace(
-        p.DatabaseTable(name=x, schema=y) >> c.UnboundTable(name=x, schema=y)
-    )
-
-
 def get_mutation_exprs(exprs: list[ir.Expr], table: ir.Table) -> list[ir.Expr | None]:
     """Return the exprs to use to instantiate the mutation."""
     # The below logic computes the mutation node exprs by splitting the

ibis/expr/types/core.py

@@ -589,9 +589,10 @@ def to_torch(
 
     def unbind(self) -> ir.Table:
         """Return an expression built on `UnboundTable` instead of backend-specific objects."""
-        from ibis.expr.analysis import substitute_unbound
+        from ibis.expr.analysis import p, c, _
 
-        return substitute_unbound(self.op()).to_expr()
+        rule = p.DatabaseTable >> c.UnboundTable(name=_.name, schema=_.schema)
+        return self.op().replace(rule).to_expr()
 
     def as_table(self) -> ir.Table:
         """Convert an expression to a table."""