what is the error in the function?

Dear Sirs:

Please I have a function as:

create function nr_renewLease(varchar(15),interval)
returns integer as '
DECLARE
 local_address ALIAS FOR $1;
 lease_duration ALIAS FOR $2;
BEGIN
  update nr_lease set expires=now()+lease_duration where
  address=local_address;
END;
return 1;
'
language 'plpgsql';

When I called this function so:

select nr_renewlease('111.111.111.111','50 seconds')

I get the follow error :

ERROR:  Function 'nr_renewlease(unknown, unknown)' does not
exist Unable to identify a function that satisfies the given
argument types You may need to add explicit typecasts.

I don't know where is the fail.

I will thank if you can help me to clarify this.

Regards,

Ernesto

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