related to jupyter-widgets/ipyleaflet#414

The problem is here: https://github.com/jupyter-widgets/ipyleaflet/blob/12ebba78899966a05245ee0f16e2872c26e4ae6a/ipyleaflet/leaflet.py#L316 Not in this package. Thanks though! 👍

Well the line doesn't hurt, I actually remove the dtype argument on my side, but the warning is still there:

[hidden]/lib/python3.7/site-packages/ipyleaflet-0.11.3-py3.7.egg/ipyleaflet/leaflet.py:316: DeprecationWarning: metadata {'dtype': None} was set from the constructor. With traitlets 4.1, metadata should be set using the .tag() method, e.g., Int().tag(key1='value1', key2='value2')
  data = Dataset().tag(sync=True, to_json=ds_x_to_json)

Ah. I see the issue:

• This definition of dtype should be move to the parent:

  traittypes/traittypes/traittypes.py

  Line 277 in 0a030b9

  dtype = None

• The parent init should take a dtype argument, and use that to set self.dtype:

  traittypes/traittypes/traittypes.py

  Line 237 in 0a030b9

  def __init__(self, default_value=Empty, allow_none=False, klass=None, **kwargs):

sounds legit
you want me to do the PR or is it faster for you to just commit it?

I'm doing a web edit

Xref #41.

@vidartf
The issue (warning) is still there; are you planning to merge your PR?