Restore input checker docs (#941)

* restore lost input checker docs
* render docs on workflow dispatch

Author: jpn--

.github/workflows/branch-docs.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   docbuild:
-    if: "contains(github.event.head_commit.message, '[makedocs]') && (github.repository_owner != 'ActivitySim') && (github.ref_name != 'develop')"
+    if: "github.event_name == 'workflow_dispatch' || (contains(github.event.head_commit.message, '[makedocs]') && (github.repository_owner != 'ActivitySim') && (github.ref_name != 'develop'))"
     # develop branch docs are built at the end of the core test workflow, regardless of repository owner or commit message flags
     name: ubuntu-latest py3.10
     runs-on: ubuntu-latest

docs/dev-guide/components/index.rst

@@ -6,6 +6,7 @@ Components
 
 .. toctree::
     :maxdepth: 1
+   input_checker
    initialize
    initialize_los
    initialize_tours

docs/dev-guide/components/input_checker.md

@@ -0,0 +1,54 @@
+(input_checker)=
+# Input Checker
+
+The input checker is an optional model that will ensure the inputs are as expected according to the
+configuration of the user. This model does not have any connection to downstream models and does not
+add anything to the ActivitySim pipeline.  It is intended to be run at the very start of every ActivitySim
+run to quickly examine whether the input data aligns with the user's expectations.
+
+The input checker is built on the Pandera python package. Users are responsible for writing the
+Pandera code that will perform the checks they would like to be performed. By allowing the user to
+write python code, they are provided with maximum flexiblity to check their input data.  (Pydantic
+was also explored as a potential technology choice for input checker implementation. Pydantic
+development got as far as performing checks and outputting errors, but further development around
+reporting warnings and more in-depth testing was dropped in favor of the Pandera approach. The
+in-development code has remained as-is in the repository in the event future data model development
+favors this approach.)
+
+If any checks fail, ActivitySim will crash and direct you to the output input_checker.log file which
+will provide details of the checks that did not pass. The user can also setup checks to output
+warnings instead of fatal errors. Warning details will be output to the input_checker.log file for
+user review and documentation. Syntax examples for both errors and warnings are demonstrated in the
+[`prototype_mtc_extended`] and [`production_semcog`] examples.
+
+Setup steps for new users:
+  * Copy the data_model directory in the [`prototype_mtc_extended`] or
+    [`production_semcog`] example folder to your setup space. You will need the enums.py and
+    input_checks.py scripts. The additional input_checks_pydantic_dev.py script in
+    [`prototype_mtc_extended`] is there for future development and can be discarded.
+  * Modify the input_checker.py to be consistent with your input data. This can include changing
+    variable names and adding or removing checks.  The amount and types of checks to perform are
+    completely up to you! Syntax is shown for many different checks in the example.
+  * Modify enums.py to be consistent with your implesmentation by changing / adding / removing variable
+    definitions.
+  * Copy the input_checker.yaml script from [`prototype_mtc_extended`] or
+    [`production_semcog`] configs into your configs
+    directory. Update the list of data tables you would like to check in the input_checker.yaml
+    file. The "validator_class" option should correspond to the name of the corresponding class in
+    the input_checker.py file you modified in the above step.
+  * Add the input_checker model to the models option in your settings.yaml file to include it in the
+    model run. When running activitysim, you will also need to include the name of the data_model
+    directory from the first step, e.g. activitysim run -c configs -d data -o outout --data_model
+    data_model.
+
+```{note}
+If you are running ActivitySim with the input checker module active, you must supply
+a --data_model argument that points to where the input_checks.py file exists!
+```
+
+## Implementation
+
+```{eval-rst}
+.. automodule:: activitysim.abm.models.input_checker
+   :members:
+```