capybara/virtualenv/lib/python2.7/site-packages/pip/_vendor/_markerlib/markers.py
def compile(marker):
    """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]
def compile(marker):
    """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]
Return compiled marker as a function accepting an environment dict.