code: def cite(self, max_authors=5):
          
          citation_data = {
              'title': self.title,
              'authors': self.authors_et_al(max_authors),
              'year': self.year,
              'journal': self.journal,
              'volume': self.volume,
              'issue': self.issue,
              'pages': self.pages,
          }
          citation = "{authors} ({year}). {title} {journal}".format(
              **citation_data)
  
          if self.volume and self.issue and self.pages:
              citation += " {volume}({issue}): {pages}.".format(**citation_data)
          elif self.volume and self.issue:
              citation += " {volume}({issue}).".format(**citation_data)
          elif self.volume and self.pages:
              citation += " {volume}: {pages}.".format(**citation_data)
          elif self.volume:
              citation += " {volume}.".format(**citation_data)
          elif self.pages:
              citation += " {pages}.".format(**citation_data)
          else:
              citation += "."
  
          return citation
docs: Return string with a citation for the record, formatted as:
          '{authors} ({year}). {title} {journal} {volume}({issue}): {pages}.'