osxphotos export: add to exported images keyword "person:PersonName_A" based on Photos Faces/People information

persons.py

""" Custom python function as an osxphotos template filter 

    Use as an option to osxphotos export template in format:
    "{template_field|sort|persons.py::myfilter}"

    For example:  
    osxphotos export /path/to/export --export-by-date --exiftool --exiftool-merge-keywords --keyword-template  "{keyword}"  --keyword-template "{person|sort|function:persons.py::myfilter}"

    The filter function will receive a list of strings even if the template renders to a single value.  
    You should expect a list and return a list and be able to handle multi-value templates like {keyword}
    as well as single-value templates like {original_name}
"""
from typing import List


def myfilter(values: List[str]) -> List[str]:
    """Custom filter to add keywords in the format person:Person for filtered persons"""
    filtered_persons = ["PersonNamed_A", "PersonNamed_B", "PersonNamed_C", "PersonNamed_D"]  # Persons to include in the list

    values = ["person:" + person for person in values if person in filtered_persons]
    
    return values