string formatting</a> syntax. The format must use parenthesized
notation to map to the subfield code. This currently restricts the
support of <code>output_pattern</code> to non-repeatable
subfields</p>
@param tag: the tag code of the field that is to be printed
@param instances_separator: a separator between instances of field
@param subfields_separator: a separator between subfields of an instance
@param limit: the maximum number of values to display.
@param extension: a text printed at the end if 'limit' has been exceeded
@param output_pattern: when specified, prints the subfields of each instance according to pattern specified as parameter (following Python string formatting convention)