.goldprice_base_url     Returns the base url for the gold price
                        endpoint.
.rates_base_url         Returns the base url for the rates endpoint.
.send_gold_endpoint_request
                        Sends a request and parses the gold price
                        endpoint response.
.send_rates_endpoint_request
                        Sends a request and parses the rates endpoint
                        response.
.send_tables_endpoint_request
                        Sends a request and parses the tables endpoint
                        response.
.tables_base_url        Returns the base url for the tables endpoint.
add_json_format         Adds the json formatting option to the passed
                        url request.
add_path_part           Adds a path part to the given url
create_request          Creates a request with the given path parts.
                        The json format argument is included by
                        default.
get_current_exchangerate
                        Retrieves the current exchange rate for the
                        given currency.
get_current_exchangerate_table
                        Retrieves the current exchange rate table.
get_current_goldprice   Retrieves the current gold price.
get_exchangerate_from   Retrieves the exchange rate from a specific
                        date.
get_exchangerate_from_interval
                        Retrieves the exchange rates from a specific
                        interval.
get_exchangerate_table_from
                        Retrieves the exchange rate table from a
                        specific date.
get_exchangerate_tables_from_interval
                        Retrieves the exchange rate tables from a
                        specific interval.
get_goldprice_from      Retrieves the gold price from a specific date.
get_goldprice_from_interval
                        Retrieves the gold prices from a specific
                        interval.
get_last_n_exchangerate_tables
                        Retrieves the last n exchange rate tables.
get_last_n_exchangerates
                        Retrieves the last n exchange rates.
get_last_n_goldprices   Retrieves the last n gold prices.
get_todays_exchangerate
                        Retrieves the exchange rate that was published
                        today.
get_todays_exchangerate_table
                        Retrieves the exchange rate table that was
                        published today.
get_todays_goldprice    Retrieves the gold price that was published
                        today.
is_count                Checks if an object is a positive integer.
is_date                 Checks if an object is a date object.
is_integer              Checks if an object is an integer.
is_nbp_api_response     Checks whether the given object is of the class
                        nbp_api_response.
nbp_api_base_url        Returns the base url of the nbp api.
