title: subsetting anndata on basis of louvain clusters
body: <p>I want to subset anndata on basis of clusters, but i am not able to understand how to do it.</p>
  <p>I am running scVelo pipeline, and in that i ran <code>tl.louvain</code> function to cluster cells on basis of louvain. I got around 32 clusters, of which cluster 2 and 4 is of my interest, and i have to run the pipeline further on these clusters only. (Initially i had the loom file which i read in scVelo, so i have now the anndata.)</p>
  <p>I tried using <code>adata.obs[&quot;louvain&quot;]</code> which gave me the cluster information, but i need to write a new anndata with only 2 clusters and process further.</p>
  <p>Please help on how to subset anndata. Any help is highly appreciated. (Being very new to it, i am finding it difficult to get)</p>