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##### SUMMARY
<!--- Explain the problem briefly below -->
Ansible documents a fact_caching_prefix option for the jsonfile cache plugin. It does not appear to do anything. Also, the fact_caching_connection option is documented as `_uri` rather than `_connection`.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
jsonfile

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.8
  config file = /home/mark/src/ansible/ansible2/ansible.cfg
  configured module search path = [u'/home/mark/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /home/mark/src/ansible-playground/venv-2.9/local/lib/python2.7/site-packages/ansible
  executable location = /home/mark/src/ansible-playground/venv-2.9/bin/ansible
  python version = 2.7.12 (default, Oct  8 2019, 14:14:10) [GCC 5.4.0 20160609]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Ubuntu

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->


##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

pass
    @abstractmethod
    def contains(self, key):
        pass
    @abstractmethod
    def delete(self, key):
        pass
    @abstractmethod
    def flush(self):
        pass
    @abstractmethod
    def copy(self):
        pass
class BaseFileCacheModule(BaseCacheModule):
    """
    A caching module backed by file based storage.
    """
    def __init__(self, *args, **kwargs):
        try:
            super(BaseFileCacheModule, self).__init__(*args, **kwargs)
            self._cache_dir = self._get_cache_connection(self.get_option('_uri'))
            self._timeout = float(self.get_option('_timeout'))
        except KeyError:
            self._cache_dir = self._get_cache_connection(C.CACHE_PLUGIN_CONNECTION)
            self._timeout = float(C.CACHE_PLUGIN_TIMEOUT)
        self.plugin_name = resource_from_fqcr(self.__module__)
        self._cache = {}
        self.validate_cache_connection()
    def _get_cache_connection(self, source):