Retrieves morphological forms of words of the keyphrase and of each synonym phrase using the function that caches
the results of previous calls of this function.

@param {string} keyphrase The paper's keyphrase.
@param {string} synonyms The paper's synonyms.
@param {string} language The paper's language.
@param {Object} morphologyData The available morphology data to be used by the getForms function (language specific).

@returns {Object} Object with an array of keyphrase forms and an array of arrays of synonyms forms.
function collectForms( keyphrase, synonyms, language = "en", morphologyData ) {
	const collectFormsWithMorphologyData = primeMorphologyData( morphologyData );

	return collectFormsWithMorphologyData( keyphrase, synonyms, language );
}