How to use the pyfakefs.fake_filesystem_unittest.Patcher function in pyfakefs

def setup(self):
        """Setup before each method"""
        config_data = basic_streamalert_config()

        self.fs_patcher = fake_filesystem_unittest.Patcher()
        self.fs_patcher.setUp()

        self.fs_patcher.fs.create_file(
            '/conf/global.json', contents=json.dumps(config_data['global']))
        self.fs_patcher.fs.create_file(
            '/conf/threat_intel.json', contents=json.dumps(config_data['threat_intel']))
        self.fs_patcher.fs.create_file(
            '/conf/normalized_types.json', contents=json.dumps(config_data['normalized_types']))
        self.fs_patcher.fs.create_file(
            '/conf/lambda.json', contents=json.dumps(config_data['lambda']))
        self.fs_patcher.fs.create_file(
            '/conf/clusters/prod.json', contents=json.dumps(config_data['clusters']['prod']))

        # Create the config instance after creating the fake filesystem so that
        # CLIConfig uses our mocked config files instead of the real ones.
        self.config = CLIConfig()

def setup(self):
        """Setup before each method"""
        config_data = basic_streamalert_config()

        self.fs_patcher = fake_filesystem_unittest.Patcher()
        self.fs_patcher.setUp()

        self.fs_patcher.fs.create_file(
            '/conf/global.json', contents=json.dumps(config_data['global']))
        self.fs_patcher.fs.create_file(
            '/conf/threat_intel.json', contents=json.dumps(config_data['threat_intel']))
        self.fs_patcher.fs.create_file(
            '/conf/normalized_types.json', contents=json.dumps(config_data['normalized_types']))
        self.fs_patcher.fs.create_file(
            '/conf/lambda.json', contents=json.dumps(config_data['lambda']))
        self.fs_patcher.fs.create_file(
            '/conf/clusters/prod.json', contents=json.dumps(config_data['clusters']['prod']))

        # Create the config instance after creating the fake filesystem so that
        # CLIConfig uses our mocked config files instead of the real ones.
        self.config = CLIConfig()

def fs(request):
    """ Fake filesystem. """
    patcher = Patcher()
    patcher.setUp()
    request.addfinalizer(patcher.tearDown)
    return patcher.fs

def setup(self):
        """Setup before each method"""
        config_data = basic_streamalert_config()

        self.fs_patcher = fake_filesystem_unittest.Patcher()
        self.fs_patcher.setUp()

        self.fs_patcher.fs.CreateFile('/conf/global.json',
                                      contents=json.dumps(config_data['global']))
        self.fs_patcher.fs.CreateFile('/conf/lambda.json',
                                      contents=json.dumps(config_data['lambda']))
        self.fs_patcher.fs.CreateFile('/conf/clusters/prod.json',
                                      contents=json.dumps(config_data['clusters']['prod']))

        # Create the config instance after creating the fake filesystem so that
        # CLIConfig uses our mocked config files instead of the real ones.
        self.config = CLIConfig()

def fs(request):
    """ Fake filesystem. """
    if hasattr(request, 'param'):
        # pass optional parameters via @pytest.mark.parametrize
        patcher = Patcher(*request.param)
    else:
        patcher = Patcher()
    patcher.setUp()
    tokenize._builtin_open = patcher.original_open
    yield patcher.fs
    patcher.tearDown()

import os
import sys

# Path hacking, for vendored pyfakefs.
sys.path.insert(0, os.path.abspath(os.path.dirname(__file__)))

import chardet
import bucketstore
from pyfakefs import fake_filesystem as fake_fs
from pyfakefs.fake_filesystem_unittest import Patcher
from pyfakefs import mox3_stubout, fake_filesystem, fake_pathlib, fake_filesystem_shutil


class S3Patcher(Patcher):
    """docstring for S3Patcher"""
    def __init__(self, filesystem):
        super(S3Patcher, self).__init__()
        self.fs = filesystem

    def _refresh(self):
        if self._stubs is not None:
            self._stubs.smart_unset_all()
        self._stubs = mox3_stubout.StubOutForTesting()

        for name in self._fake_module_classes:
            self._fake_modules[name] = self._fake_module_classes[name](self.fs)
        self._fake_modules['path'] = self._fake_modules['os'].path
        self.fake_open = fake_filesystem.FakeFileOpen(self.fs)

        self._isStale = False