def getCache(module):
    """
    Compute all the possible loadable plugins, while loading as few as
    possible and hitting the filesystem as little as possible.

    @param module: a Python module object.  This represents a package to search
    for plugins.

    @return: a dictionary mapping module names to L{CachedDropin} instances.
    """
    allCachesCombined = {}
    mod = getModule(module.__name__)
    # don't want to walk deep, only immediate children.
    buckets = {}
    # Fill buckets with modules by related entry on the given package's
    # __path__.  There's an abstraction inversion going on here, because this
    # information is already represented internally in twisted.python.modules,
    # but it's simple enough that I'm willing to live with it.  If anyone else
    # wants to fix up this iteration so that it's one path segment at a time,
    # be my guest.  --glyph
    for plugmod in mod.iterModules():
        fpp = plugmod.filePath.parent()
        if fpp not in buckets:
            buckets[fpp] = []
        bucket = buckets[fpp]
        bucket.append(plugmod)
    for pseudoPackagePath, bucket in iteritems(buckets):
        dropinPath = pseudoPackagePath.child('dropin.cache')
        try:
            lastCached = dropinPath.getModificationTime()
            with dropinPath.open('r') as f:
                dropinDotCache = pickle.load(f)
        except:
            dropinDotCache = {}
            lastCached = 0

        needsWrite = False
        existingKeys = {}
        for pluginModule in bucket:
            pluginKey = pluginModule.name.split('.')[-1]
            existingKeys[pluginKey] = True
            if ((pluginKey not in dropinDotCache) or
                (pluginModule.filePath.getModificationTime() >= lastCached)):
                needsWrite = True
                try:
                    provider = pluginModule.load()
                except:
                    # dropinDotCache.pop(pluginKey, None)
                    log.err()
                else:
                    entry = _generateCacheEntry(provider)
                    dropinDotCache[pluginKey] = entry
        # Make sure that the cache doesn't contain any stale plugins.
        for pluginKey in list(dropinDotCache.keys()):
            if pluginKey not in existingKeys:
                del dropinDotCache[pluginKey]
                needsWrite = True
        if needsWrite:
            try:
                dropinPath.setContent(pickle.dumps(dropinDotCache))
            except OSError as e:
                log.msg(
                    format=(
                        "Unable to write to plugin cache %(path)s: error "
                        "number %(errno)d"),
                    path=dropinPath.path, errno=e.errno)
            except:
                log.err(None, "Unexpected error while writing cache file")
        allCachesCombined.update(dropinDotCache)
    return allCachesCombined

    Compute all the possible loadable plugins, while loading as few as
    possible and hitting the filesystem as little as possible.

    @param module: a Python module object.  This represents a package to search
    for plugins.

    @return: a dictionary mapping module names to L{CachedDropin} instances.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/plugin.py