Signals Notebook: "<Field name>is not a valid unit." warning message during bulk material import mapping

When performing bulk imports from CSV files, users may encounter the following warning flag when mapping columns that contain unit values: "<Field name>is not a valid unit." The behavior is seen when:
     1. The data in the CSV file already contains unit values in the first record (e.g., "95%" for Purity)
     2. The user selects a specific unit (e.g., "%") from the unit dropdown instead of selecting "Unit in value"

Cause: This is the expected behavior of the application for fields fields that accept units, including Purity and Amount fields. This warning is informational and indicates a potential conflict between units in the data and the selected unit in the interface.

Solution: To avoid seeing this warning:
     1. Select "Unit in value" from the dropdown if your data already includes unit information
     2. Only select specific units when your data contains numeric values without units