Get an entry from a BibTeX file.

    :param filename: The name of the BibTeX file.
    :param identifier: An id of the entry to fetch, in the BibTeX file.
    :param ignore_fields: An optional list of fields to strip from the BibTeX \
            file.

    :returns: A ``bibtexparser.BibDatabase`` object representing the \
            fetched entry. ``None`` if entry was not found.

def get_entry(filename, identifier, ignore_fields=None):
    """
    Get an entry from a BibTeX file.

    :param filename: The name of the BibTeX file.
    :param identifier: An id of the entry to fetch, in the BibTeX file.
    :param ignore_fields: An optional list of fields to strip from the BibTeX \
            file.

    :returns: A ``bibtexparser.BibDatabase`` object representing the \
            fetched entry. ``None`` if entry was not found.
    """
    # Handle default argument
    if ignore_fields is None:
        ignore_fields = []

    return get_entry_by_filter(filename,
                               lambda x: x["ID"] == identifier,
                               ignore_fields)