new_contents: from .util import collect
  from .coretypes import *
  
  # https://github.com/ContinuumIO/datashape/blob/master/docs/source/types.rst
  
  dimension_types = (Fixed, Var, Ellipsis)
  
  def isdimension(ds):
      """ Is a component a dimension?
  
      >>> isdimension(Fixed(10))
      True
      >>> isdimension(Var())
      True
      >>> isdimension(int32)
      False
      """
      return isinstance(ds, dimension_types)
  
subject: add isdimension