code: def import_attr(module_name, attr_name):
      
      module = import_module(module_name)
  
      try:
          return getattr(module, attr_name)
      except AttributeError as err:
          raise UnknownCallableError(str(err))
docs: Given a dotted Python path & an attribute name, imports the module &
      returns the attribute.
  
      If not found, raises ``UnknownCallableError``.
  
      Ex::
  
          choice = import_attr('random', 'choice')
  
      :param module_name: The dotted Python path
      :type module_name: string
  
      :param attr_name: The attribute name
      :type attr_name: string
  
      :returns: attribute