title: Get list of files from s3 bucket with a particular substring
body: <p>I have an s3 bucket that has various kinds of file.</p>
  
  <p>Example - <code>abc.csv, def.tsv, ghi_sub_jkl.avro, mno_sub_pqrs.avro and others.</code></p>
  
  <p>I need a function that can give me a list of files that have a particular substring in its filename. 
  In the above example I need the files having "sub" as the substring.</p>
  
  <p>Therefore, the output list must contain - <code>['ghi_sub_jkl.avro', 'mno_sub_pqrs.avro']</code></p>
  
  <p>Is there a way to do it?</p>