Changed to_dict to call all callable values when their key is in field_names.
This is useful for instance when exporting role instances and you want to export document_name.
# use glob syntax.
syntax: glob
*.pyc
*.zip
*~
.project
.pydevproject
app.yaml
build
tests/coverageResults
*,cover
tests/.coverage
*.git
*.egg-info
eggs
parts
.installed.cfg
bin
develop-eggs
.gitignore
.DS_Store
.settings