code: def get_entry(filename, identifier, ignore_fields=None):
      
      # Handle default argument
      if ignore_fields is None:
          ignore_fields = []
  
      return get_entry_by_filter(filename,
                                 lambda x: x["ID"] == identifier,
                                 ignore_fields)
docs: 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.