The default value for the columns input includes lon_lowestmode and lat_lowestmode because they are necessary for subsetting. However, if a user supplies their own value for columns that does not explicitly include both of those columns, then the code throws an exception: AttributeError: 'DataFrame' object has no attribute 'lon_lowestmode'

This forces the user to explicitly specify those 2 columns, but they should not have to do so.

Acceptance Criteria

• When the user specifies a value for the column input, lon_lowestmode and lat_lowestmode should be implicitly added to the list of columns, if missing
• Default value for columns should drop the explicit inclusion of these 2 columns
• Subsetting should succeed when using the new default columns value
• Subsetting should succeed when using a custom columns value that does not explicitly include either column