code: def get_collections(db, collection=None, prefix=None, suffix=None):
      '''
      Returns a sorted list of collection names found in ``db``.
      Arguments:
          db (Database): A pymongo Database object. Can be obtained
              with ``get_db``.
          collection (str): Name of a collection. If the collection is
              present in the MongoDB database, a single-element list will
              be returned with the collecion name. If not, an empty list
              will be returned. This option is primarly included to allow
              for quick checking to see if a collection name is present.
              Default is None, which results in this option being ignored.
          prefix (str): If supplied, only collections that begin with
              ``prefix`` will be returned.
          suffix (str): If supplied, only collections that end with
              ``suffix`` will be returned.
      Returns:
          list: A sorted list of collection names.
      '''
      if collection is not None:
          return [collection, ]
      collections = db.collection_names(include_system_collections=False)
      if prefix is not None:
          collections = [c for c in collections if c.startswith(prefix)]
      if suffix is not None:
          collections = [c for c in collections if c.endswith(suffix)]
      return sorted(collections)