code: def get_field(self, name):
          
          # TODO could use a generator here
          prog = re.compile(name)
          l = []
          for i in self.get_classes():
              for j in i.get_fields():
                  if prog.match(j.get_name()):
                      l.append(j)
          return l
docs: Return a list all fields which corresponds to the regexp
  
          :param name: the name of the field (a python regexp)
  
          :rtype: a list with all :class:`EncodedField` objects