docs: def display_callback(self, component, **kwargs):
          """
          Display given component in this environment.
  
          .. note::
  
              To be overridden by inheriting classes
  
          An example of a introducing a custom display environment.
  
          .. doctest::
  
              import cqparts
              from cqparts.display.environment import DisplayEnvironment, map_environment
  
              def is_text_env():
                  # function that returns True if it's run in the
                  # desired environment.
                  import sys
                  # Python 2.x
                  if sys.version_info[0] == 2:
                      return isinstance(sys.stdout, file)
                  # Python 3.x
                  import io
                  return isinstance(sys.stdout, io.TextIOWrapper)
  
              @map_environment(
                  name="text",
                  order=0,  # force display to be first priority
                  condition=is_text_env,
              )
              class TextDisplay(DisplayEnvironment):
                  def display_callback(self, component, **kwargs):
                      # Print component details to STDOUT
                      if isinstance(component, cqparts.Assembly):
                          sys.stdout.write(component.tree_str(add_repr=True))
                      else:  # assumed to be a cqparts.Part
                          sys.stdout.write("%r\\n" % (component))
  
          ``is_text_env()`` checks if there's a valid ``sys.stdout`` to write to,
          ``TextDisplay`` defines how to display any given component,
          and the ``@map_environment`` decorator adds the display paired with
          its environment test function.
  
          When using :meth:`display() <cqparts.display.display>`, this display
          will be used if ``is_text_env()`` returns ``True``, and no previously
          mapped environment with a smaller ``order`` tested ``True``:
  
          .. doctest::
  
              # create component to display
              from cqparts_misc.basic.primatives import Cube
              cube = Cube()
  
              # display component
              from cqparts.display import display
              display(cube)
  
          The ``display_callback`` will be called via
          :meth:`display() <DisplayEnvironment.display>`.  So to call this
          display method directly:
  
          .. doctest::
  
              TextDisplay().display(cube)
  
          :raises: NotImplementedError if not overridden
          """
          if type(self) is DisplayEnvironment:
              raise RuntimeError(
                  ("%r is not a functional display environment, " % (type(self))) +
                  "it's meant to be inherited by an implemented environment"
              )
          raise NotImplementedError(
              "display_callback function not overridden by %r" % (type(self))
          )