def AVG(src_column):
    """
  Builtin average aggregator for groupby. Synonym for gl.aggregate.MEAN. If
  src_column is of array type, and if array's do not match in length a NoneType is
  returned in the destination column.

  Example: Get the average rating of each user.

  >>> sf.groupby("user",
  ...            {'rating_avg':gl.aggregate.AVG('rating')})

  """
    return '__builtin__avg__', [src_column]
