import re


def filter_ads_keys(cite_keys):
    """Select keys matching the pattern of ADS bibtex keys.

    The current pattern to match is: `"\d\d\d\d..............."`

    Parameters
    ----------
    cite_keys: array of string
      An array of bibtex keys

    Returns
    -------
    ads_keys: array of string
      The matching keys from cite_keys
    """

    ads_pat = re.compile("\d\d\d\d...............")
    return [key for key in cite_keys if ads_pat.match(key) is not None]