def codeChecker(wetland_type, modifiers):
    modifiers = modifiers.split(', ')
    incorrect_modifiers = []
    match_dict = {'LOBA': ['ay', 'bv', 'fm', 'fn', 'gf', 'hs', 'il', 'mr', 'ox', 'sa', 'ag'],
                  'LOFP': [],
                  'LOFR': [],
                  'LEBA': [],
                  'LEFP': [],
                  'LEFR': [],
                  'TEBA': [],
                  'TEFL': [],
                  'TEFR': [],
                  'TESL': []}
    for modifier in modifiers:
        if modifier not in match_dict[wetland_type]:
            incorrect_modifiers.append(modifier)
    return(', '.join(incorrect_modifiers))

codeChecker('LOBA', "ay, bv, hs") # input containing all valid modifiers
# will leave the field empty as there are no errors
codeChecker('LOBA', 'ay, bg, bv') # input containing one incorrect modifier
# will return 'bg'
codeChecker('LOBA', 'ay, bg, id') # input containing multiple incorrect modifiers
# will return 'bg, id'