human
Complete this python program:
def compile(marker):
assistant
#Here is the Python code you requested.

    """Return compiled marker as a function accepting an environment dict.
    """
    try:
        return _cache[marker]
    except KeyError:
        pass
    if (not marker.strip()):
        def marker_fn(environment=None, override=None):
            ''
            return True
    else:
        compiled_marker = compile_marker(parse_marker(marker))
        def marker_fn(environment=None, override=None):
            'override    updates    environment'
            if (override is None):
                override = {}
            if (environment is None):
                environment = default_environment()
            environment.update(override)
            return eval(compiled_marker, environment)
    marker_fn.__doc__ = marker
    _cache[marker] = marker_fn
    return _cache[marker]