notebook: invalid variable names for `%%cell_to_module --execute`

[zilto]

If you're using %%cell_to_module my_module --execute it will try to push nodes back into the user namespace. This fails if the node includes a . in its name (internal nodes of @pipe_input, @pipe_output, @mutate, @load_from, etc.)

The following allows to only execute and push the specified nodes, and avoid this issue:

## cell 1
final_vars = ["foo", "bar"]

## cell 2
%%cell_to_module my_dataflow --execute final_vars
from hamilton.function_modifiers import pipe_input, step

def foo() -> dict:
  return {...}

def _invert_mapping(d: dict) -> dict:
   return {v: k for k, v in d.items()}

@pipe_input(step(_invert_mapping))
def bar(foo: dict) -> dict:
  return foo

However, this will when calling %%cell_to_module --execute without an argument because it tries to execute and push all nodes (including the generated bar.with_invert_mapping).

Proposed solution

Before pushing back results to the user namespace, check if the name includes a . and replace by __. The double underscore is a good option because Hamilton already ignores __ suffix when parsing node names. Using single underscore is likely to cause naming conflicts with other user-created nodes

[zilto]

Apparently this I had fixed this in #917