Python Command runs but does show completion in Jupyter Notebook


Creating databases via Python and Jupyter notebooks.
For the most part working well and am using neo python driver.
Here is where I am having some trouble. I have a data frame with the data to bring into Neo4J, a document number and a date. Some of the document do not have valid dates and the value in the field is "null" as a string. It setting the data I would like to trap for these and ignore that row of data.
If I run the code below it does not seem to complete and I am using the Jupyter signal in the line number as a gauge. When the cell is executing it has an "*". Using that the cell never completes. If I go to browser in Neo4J and examine the nodes the date fields seem correctly populated. Any idea why it would not complete?

def set_patent_date(tx,case,issue):
    result ="MATCH (a:patent{num:$case}) set a.issued = date($issue)", case=case, issue=issue)

with driver.session() as session:

    for patent in PAT.itertuples():
        if != 'null':
            testcase = session.write_transaction(set_patent_date,patent.num,