Cell magics cannot handle --help when the cell is empty

[krlawrence]

It is not possible to get help using a command like %%gremlin --help unless there is something else in the cell on another line. It would be nice if that was not required. Perhaps for argument processing we should move from directly using argparse to using @magic_arguments() decorators

Also an exception is displayed beneath the help text.

[austinkline]

Reference doc: https://ipython.readthedocs.io/en/stable/api/generated/IPython.core.magic_arguments.html?highlight=magic_arguments#module-IPython.core.magic_arguments

[joywa]

Impact: Improve getting started experience.

Currently, users have to include a Gremlin query underneath for the help to show up, which is not ideal for beginners.

%%gremlin --help

g.V().limit(10)