pymbolic.compiler doesn't sanitize variable names

>>> from pymbolic import parse, compile
>>> compile(parse("with"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "build/bdist.macosx-10.11-x86_64/egg/pymbolic/compiler.py", line 111, in __init__
  File "build/bdist.macosx-10.11-x86_64/egg/pymbolic/compiler.py", line 138, in _compile
  File "<string>", line 1
    lambda with: with
              ^
SyntaxError: invalid syntax