*Join <code>patent</code> data to <code>assignee</code> data, creating <code>firstjoin_cleaned</code>
*Join <code>firstjoin_cleaned</code> data to <code>matchassignee</code> data, creating <code>secondjoin_cleaned</code>*Join <code>secondjoin_cleaned</code> data to <code>venturepatentmatched</code> data, creating <code>fourthjoin_cleaned</code>