'Generate output in Jupyter/Zeppelin notebook cells.
Calling ``output_notebook`` not clear the effects of any other calls
to ``output_file``, etc. It adds an additional output destination
(publishing to notebook output cells). Any other active output modes
continue to be active.
Returns:
None'

def output_notebook(self, notebook_type='jupyter'):

    self._notebook = True
    self.notebook_type = notebook_type
