code: function(languageSlug, versificationSlug) {
              let result = query('' +
                  'select vn.name, v.slug, v.id from versification_name as vn' +
                  ' left join versification as v on v.id=vn.versification_id' +
                  ' left join source_language as sl on sl.id=vn.source_language_id' +
                  ' where sl.slug=? and v.slug=?', [languageSlug, versificationSlug]);
              if(result.length > 0) {
                  return result[0];
              }
              return null;
          }
docs: Returns a versification.
  
  @param languageSlug {string}
  @param versificationSlug {string}
  @returns {{}|null}