Take the two % out of this line if '%Notes_SHLs%' in layer.dataSource:

If you want to check if a specific string is within a variable, you need to exclude the % wildcard symbols

if 'Notes_SHLs' in layer.dataSource:

Take the two % out of this line if '%Notes_SHLs%' in layer.dataSource:

If you want to check if a specific string is within a variable, you need to exclude the % wildcard symbols

if 'Notes_SHLs' in layer.dataSource:

In response to your comment below, do a print on that layer.dataSource rather than the if to determine what is actually there:

if layer.supports("DATASOURCE"):
    print layer.dataSource