Associate Content with input variable

[IzaakWN]

Right now each Content model is assumed to be in the same order as the given input variables, but in some cases an input variable might not be used, or have a different order.

I would propose to add an input(s) attribute to Binning, MultiBinning and Category, e.g.

class Binning(Model):
    nodetype: Literal["binning"]
    edges: List[float]
    "Edges of the binning, where edges[i] <= x < edges[i+1] => f(x, ...) = content[i](...)"
    content: List[Content]
    input: str

class MultiBinning(Model):
    """N-dimensional rectangular binning"""
    nodetype: Literal["multibinning"]
    edges: List[List[float]]
    "Bin edges for each input"
    content: List[Content]
    inputs: List[str]

class Category(Model):
    nodetype: Literal["category"]
    keys: List[Union[str,int]]
    content: List[Content]
    input: str

such that the evaluator or a human reader knowns which Content block belongs to which input variable, no matter the order.

JSON files would for example look like

{
  'version': 0,
  'name': "test",
  'inputs': [
    {'name': "eta", 'type': "real", 'description': "tau eta"},
    {'name': "pt",  'type': "real", 'description': "tau pt"},
    {'name': "genmatch",  'type': "int", 'description': "genmatch"},
  ],
  'output': {'name': "weight", 'type': "real"},
  'data': {
    'nodetype': "category",
    'input': "genmatch",
    'keys': [1,2],
    'content': [
      { 'nodetype': "binning", # genmatch == 1
         'input': "eta",
         'edges': [0.0,1.5,2.4],
         'content': [0.9,1.1]
      },
      { 'nodetype': "binning", # genmatch == 2
         'input': "pt",
         'edges': [20.0,40.0,100.0],
         'content': [0.9,1.1]
      },
    ],
  },
}

[nsmith-]

I was initially worried because I expected to pop input arguments in the evaluator as it descends the tree. But instead I decided to pass the whole set of inputs all the way through the tree (since Formula leaf nodes may need an arbitrary input)
So this should be simple. In fact, the Formula node can probably use names instead of indices as well, resolving them in instantiation in the evaluator for speed.