code: def get_assignments(self, site):
          
          tools = self.get_tools(site)
          assignment_tool_filter = [x.href for x in tools if x.name == 'assignment-grades']
          if not assignment_tool_filter:
              return []
          assignment_tool_url = assignment_tool_filter[0].href
          response = self._session.get(assignment_tool_url)
          response.raise_for_status()
          iframes = self._html_iface.get_iframes(response.text)
          iframe_url = ''
          for frame in iframes:
              if frame['title'] == 'Assignments ':
                  iframe_url = frame['src']
          if iframe_url == '':
              print "WARNING: NO ASSIGNMENT IFRAMES FOUND"
          response = self._session.get(iframe_url)
          response.raise_for_status()
          assignment_dict_list = self._html_iface.get_assignments(response.text)
          return [TSquareAssignment(**x) for x in assignment_dict_list]
docs: Gets a list of assignments associated with a site (class). Returns
          a list of TSquareAssignment objects.
          @param site (TSquareSite) - The site to use with the assignment query
  
          @returns - A list of TSquareSite objects. May be an empty list if
                     the site has defined no assignments.