Read selected fields from the metadata of some given input atlases. By default, the reader
will read all fields and dump them to stdout. The user may supply additional options to filter
for specific fields. For example, if the user only cares about the 'size' field, they may
supply the '--size' option to filter for that field. Or if the user would only like to see the
'code-version' and 'data-version' fields, they may supply '--code-version' and '--data-version'.
