Feature/traitlets refactor

[mpu-creare]

This modifies the way we use Traitlets. It inegrates more tightly with traitlets, requiring traits to be tagged. This tagging can the be used to more accurately and robustly create pipelines.

Also adding a large amount of documentation in the PR.

[mpu-creare]

I'd like this one merged in sooner than later so we can start working using the same methodology.

[coveralls]

Pull Request Test Coverage Report for Build 133

• 280 of 354 (79.1%) changed or added relevant lines in 13 files are covered.
• 15 unchanged lines in 6 files lost coverage.
• Overall coverage increased (+4.5%) to 64.65%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
podpac/datalib/smap.py	0	1	0.0%
podpac/core/algorithm/coord_select.py	28	29	96.55%
podpac/core/algorithm/signal.py	20	21	95.24%
podpac/core/pipeline.py	0	1	0.0%
podpac/core/data/data.py	15	17	88.24%
podpac/core/algorithm/test/test_algorithm.py	1	5	20.0%
podpac/core/compositor.py	12	16	75.0%
podpac/core/algorithm/algorithm.py	9	14	64.29%
podpac/core/data/type.py	29	35	82.86%
podpac/core/algorithm/test/test_signal.py	57	64	89.06%

Files with Coverage Reduction	New Missed Lines	%
podpac/core/authentication.py	1	36.36%
podpac/core/test/test_node.py	1	97.14%
podpac/core/coordinate/coordinate.py	1	53.02%
podpac/core/compositor.py	3	31.13%
podpac/core/node.py	3	51.88%
podpac/core/coordinate/test/test_coordinate.py	6	76.01%

Totals
Change from base Build 114:	4.5%
Covered Lines:	3890
Relevant Lines:	6017

---

💛 - Coveralls

[jmilloy]

@mpu-creare This was the first thing I tried to do.

from podpac import Coordinate
from podpac.core.algorithm.algorithm import CoordData 
n = CoordData(coord_name='lat')
c = Coordinate(lat=[1, 2, 3, 4])
n.execute(c)

Here's the result:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "podpac/core/algorithm/algorithm.py", line 70, in execute
    result = self.algorithm()
  File "podpac/core/algorithm/algorithm.py", line 162, in algorithm
    coord_name = self._params['coord_name']
KeyError: u'coord_name'

Are the tagged attrs supposed to be loaded in the the _params, too? Does get_params need to be if value.metadata.get('param', False) or value.metadata.get('attr', False)? Or is it something else?

[jmilloy]

@mpu Well, no, actually I'm guessing that either

• coord_name should be tagged as a param, or
• it should be coord_name = self.coord_name (instead of coord_name = self._params['coord_name'])

[mpu-creare]

Yep, that was another mistake on my part. attrs are NOT supposed to be loaded into the params dictionary. It should have be self.coord_name. I'll fix that and the ReprojectedCoords one.

[jmilloy]

Looks great, seems pretty clear. I guess we need these two tags to be documented somewhere, probably we need a "Writing Custom Nodes" user guide and we would describe these there.

[mpu-creare]

Agreed. Feel free to start a doc stub, or assign that task to me.