Average Calculation Function

Axon Evidence records can contain numeric metadata such as file size or processing duration. Given an in-memory collection of records and a field name, calculate the arithmetic mean of that field across all records that contain it.

Formal Specification

Implement average_field(records, field).

• records is a list of dictionaries, where each dictionary represents one Axon Evidence record.
• field is a string naming the desired field.
• The selected field contains integers or floating-point numbers when present.
• Ignore records that do not contain field.
• Return the average as a floating-point number.
• At least one record contains the requested field.