title: Errors for block matrix multiplification in Spark
body: <p>I have created a coordinate matrix cmat with 9 million rows and 85K columns.  I would like to perform cmat.T * cmat operations.
  I first converted cmat to block matrix bmat:</p>
  
  <pre><code>bmat = cmat.toBlockMatrix(1000, 1000)
  </code></pre>
  
  <p>However, I got errors when performing multiply():</p>
  
  <pre><code>mtm = bmat.transpose.multiply(bmat)
  </code></pre>
  
  <p>Traceback (most recent call last):
    File "", line 1, in 
  AttributeError: 'function' object has no attribute 'multiply'</p>
  
  <p>The Spark version is 2.2.0, scale version is 2.11.8 on DataProc, Google cloud platform.
  Any suggestions on how to fix the error?</p>