title: Amazon DynamoDB Query for Items whose key contains a substring
body: <p>I am using an Amazon DynamoDB database, and I have a list of items with various strings as the key. I want to query for items whose key contains a substring. For example, if some of the keys are:
  <br>
  <br>"abcd_aaa"
  <br>"abcd_bbb"
  <br>"abcd_ccc"</p>
  
  <p>I want to query where a key contains "abcd" and these 3 items will be returned.  Is this possible?</p>