code: def get_module_source(self, fullname):
          
          tup = self._found_cache.get(fullname)
          if tup:
              return tup
  
          for method in self.get_module_methods:
              tup = method(self, fullname)
              if tup:
                  #LOG.debug('%r returned %r', method, tup)
                  break
          else:
              tup = None, None, None
              LOG.debug('get_module_source(%r): cannot find source', fullname)
  
          self._found_cache[fullname] = tup
          return tup
docs: Given the name of a loaded module `fullname`, attempt to find its
          source code.
  
          :returns:
              Tuple of `(module path, source text, is package?)`, or :data:`None`
              if the source cannot be found.