feat: dx.indicator spec

[jnumainville]

spec for #1019

I haven't really written a spec for dx before but it made sense to me to just put it in a new function with NotImplementedError.

Instead of just enabling one indicator, you can create multiple at one time with a plot by that makes subplots of indicators. This enables, for example, the creation of a new indicator automatically as a new symbol ticks in.
The default behavior is only a number if you only provide value and number+delta if you provide reference as well.
https://plotly.com/python/indicator/

Syntax is otherwise generally in line with other dx functions and most other behavior is fairly straightforward.

[mofojed]

Makes sense to me... only thing I'd like is to be able to pass in a value that I have outside of a table as well. Calculated from a user input or something.
It could be that we pump it through a table anyway, but I'd like to see an example of how to hook that up.

[jnumainville]

Makes sense to me... only thing I'd like is to be able to pass in a value that I have outside of a table as well. Calculated from a user input or something. It could be that we pump it through a table anyway, but I'd like to see an example of how to hook that up.

Added an example of putting some values in a table.
I think if we want something more comprehensive, I'd argue it's beyond the scope of this initial indicator implementation because what we would really want to do is rework what we allow passed into table for all plots. Things like dicts, lists, etc. I don't really like the idea of breaking the abstraction by passing in values directly to parameters that take columns (like value and reference) as it adds complexity and inconsistency, but I'd be open to expanding what we allow passed into table.

[dsmmcken]

stray dash

[jnumainville]

removed

[mofojed]

Looks good to me.

This has inspired me to create a utility function called dict_table for where you just want a table from a dictionary, e.g.

from deephaven import dict_table

my_table = dict_table({
  "MyValue": [my_value],
  "MyReference": [my_reference],
})

Or even just assume if it's not a list passed in, that it is just a one row table and you don't need to pass in an array explicitly, e.g.:

from deephaven import dict_table

my_table = dict_table({
  "MyValue": my_value,
  "MyReference": my_reference,
})

Don't have as control over types ... but it would be nice for creating quick tables like in this case.