title: Correct syntax with IN condition on a find() query in mongolite
body: <p>I am trying to use an IN condition to query with the mongolite package. I can get the query to work if I use the mongo console based on this page:
  <a href="https://docs.mongodb.com/manual/reference/operator/query/in/#op._S_in" rel="nofollow">https://docs.mongodb.com/manual/reference/operator/query/in/#op._S_in</a>. I've tried variations on the following in my R code, but either end up with 0 results or a syntax error:</p>
  
  <pre><code>aaContDF &lt;- mongoBirdData$find('{ "aircraftAirlineOperator": { "$in":
                                 { [ "AMERICAN AIRLINES",
                                 "CONTINENTAL AIRLINES" ] } } }',
                                 fields = '{"recordId":1, "originState":1,
                                 "aircraftAirlineOperator":1,
                                 "airportName":1}')
  </code></pre>
  
  <p>With error message:</p>
  
  <pre><code>Error: Invalid JSON object: { "aircraftAirlineOperator": { "$in":
                             { [ "AMERICAN AIRLINES",
                             "CONTINENTAL AIRLINES" ] } } }
  </code></pre>
  
  <p>The queries I've worked with have been AND conditions, haven't encountered any OR scenarios yet.  Thank you. </p>