code: def _infer_x_for_line(y):
      
      array_shape = shape(y)
  
      if len(array_shape) == 0:
          return []
      if len(array_shape) == 1:
          return arange(array_shape[0])
      if len(array_shape) > 1:
          return arange(array_shape[1])
docs: Infers the x for a line if no x is provided.