final String key = e.getKey();
            if (StringUtil.isBlank(key)) {
                return false;
            }
            return pattern.matcher(key).matches();
        }).collect(Collectors.toMap(Entry<String, String>::getKey, Entry<String, String>::getValue));
    }

    /**
     * Gets a map of environment variables.
     *

   *
   * <p>While resolving a type variable from a {@code var -> type} map, we don't care whether the
   * type variable's bound has been partially resolved. As long as the type variable "identity"
   * matches.
   *
   * <p>On the other hand, if for example we are resolving {@code List<A extends B>} to {@code
   * List<A extends String>}, we need to compare that {@code <A extends B>} is unequal to {@code <A

   *
   * <p>While resolving a type variable from a {@code var -> type} map, we don't care whether the
   * type variable's bound has been partially resolved. As long as the type variable "identity"
   * matches.
   *
   * <p>On the other hand, if for example we are resolving {@code List<A extends B>} to {@code
   * List<A extends String>}, we need to compare that {@code <A extends B>} is unequal to {@code <A

        }
        return count;
    }

    /**
     * Deletes documents in an index matching a query.
     *
     * @param index        the index name
     * @param queryBuilder the query to match documents for deletion
     * @return the number of documents deleted
     */
    public long deleteByQuery(final String index, final QueryBuilder queryBuilder) {