Whether x is fully contained in y.

def Operation(self, x, y):
    """Whether x is fully contained in y."""
    if x in y:
      return True

    # x might be an iterable
    # first we need to skip strings or we'll do silly things
    if isinstance(x, string_types) or isinstance(x, bytes):
      return False

    try:
      for value in x:
        if value not in y:
          return False
      return True
    except TypeError:
      return False