Add a close method to the DirectoryStore and N5Store

[hmaarrfk]

The ZipStore contains a close method that ensures that the file is flushed on the OS, and ready for the next line of code to use.

It wouild be nice to have noop methods for the DirectoryStore (and N5Store) to ensure that we don't have to use the following code downstream

if hasattr(store, 'close'): 
    store.close()

Minimal, reproducible code sample, a copy-pastable example if possible

import zarr
dstore = zarr.DirectoryStore('test.dir')
dstore.close()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-3-a0f668fd8b50> in <module>
----> 1 dstore.close()

AttributeError: 'DirectoryStore' object has no attribute 'close'

import zarr
zstore = zarr.ZipStore('test.zip')
zstore.close()
# All good

Version and installation information

Please provide the following:

• Value of zarr.__version__: 2.4.1.dev15+dirty

• Value of numcodecs.__version__: 0.6.4

• Version of Python interpreter: 3.8.5

• Operating system (Linux/Windows/Mac) Linux

• How Zarr was installed (e.g., "using pip into virtual environment", or "using conda"): conda-forge

[hmaarrfk]

Usage example: https://github.com/pydata/xarray/pull/4395

[joshmoore]

cc: @Carreau

[Carreau]

Opened #600 to track other advantages of having a base store that implements boilerplate methods like close().

[ManMaich0]

@joshmoore @MSanKeys963 I'm an Outreach candidate and would like to work on this.

[hmaarrfk]

I think this issue can be closed. It seems that since #600 was closed, this is no longer an issue with at least the latest version of zarr.

In [1]: import zarr
   ...: dstore = zarr.DirectoryStore('test.dir')
   ...: dstore.close()

In [2]: zarr.__version__
'2.13.3'

[jakirkham]

Thanks Mark! 🙏

Glad to hear things are working now 😄