title: How to count incoming vertices in gremlin?
body: <p>I have this Database:</p>
  
  <p>Clients => Incident => File => Filename</p>
  
  <p>Clients have an ID Incidents have an ID and a reportedOn property Files have an ID and a fileSize, mimeType, malware property Filenames have an ID Client have a outgoing Edge to Incidents (reported), incident have a outgoing Edge to file (containsFile), file have a outgoing Edge to filename (hasName).</p>
  
  <p>Here is some sample DATA:</p>
  
  <pre><code>g.addV('client').property('id','1').as('1').
    addV('incident').property('id','11').property('reportedON', '2/15/2019 8:01:19 AM').as('11').
    addV('file').property('id','100').property('fileSize', '432534').property('malwareSource', 'malware').as('100').
    addV('fileName').property('id','file.pdf').as('file.pdf').
    addE('reported').from('1').to('11').
    addE('containsFile').from('11').to('100').
    addE('hasName').from('100').to('file.pdf').iterate()
  </code></pre>
  
  <p>I am executing this query:</p>
  
  <pre><code>g.V().has('malwareSource', 'malware').as('FILE').out('hasName').as('FILENAME').select('FILE').in('containsFile').as('INCIDENT').select('FILE').valueMap().as('FILEVALUES').select('INCIDENT').valueMap().as('INCIDENTVALUES').select('FILE', 'FILEVALUES', 'FILENAME', 'INCIDENTVALUES')
  </code></pre>
  
  <p>How can I count how many incoming vertices each file with the property 'malware' has?</p>