ENH: Build API entry usage graphs (mne-tools#12013)

Author: larsoner

doc/conf.py

@@ -620,7 +620,7 @@ def __call__(self, gallery_conf, fname, when):
         r"mne\.Epochs",
         r"mne.datasets.*",
     },
-    "show_api_usage": False,  # disable for now until graph warning fixed
+    "show_api_usage": "unused",
     "api_usage_ignore": (
         "("
         ".*__.*__|"  # built-ins
@@ -688,6 +688,15 @@ def append_attr_meth_examples(app, what, name, obj, options, lines):
 
 # -- Other extension configuration -------------------------------------------
 
+# Consider using http://magjac.com/graphviz-visual-editor for this
+graphviz_dot_args = [
+    "-Gsep=-0.5",
+    "-Gpad=0.5",
+    "-Nshape=box",
+    "-Nfontsize=20",
+    "-Nfontname=Open Sans,Arial",
+]
+graphviz_output_format = "svg"  # for API usage diagrams
 user_agent = "Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/113.0.0.0 Mobile Safari/537.36"  # noqa: E501
 # Can eventually add linkcheck_request_headers if needed
 linkcheck_ignore = [  # will be compiled to regex

doc/install/contributing.rst

@@ -1027,6 +1027,11 @@ down the road. Here are the guidelines:
       nicely formatted) and the resulting output and figures will be rendered
       as part of the tutorial/example.
 
+- Examples and tutorials should execute as quickly and with as low memory usage as
+  possible while still conveying necessary information. To see current execution
+  times and memory usage, visit the `sg_execution_times page`_. To see unused API
+  entries, see the `sg_api_usage page`_.
+
 `This sample pull request`_ exemplifies many of the conventions listed above:
 it addresses only one problem; it started with an issue to discuss the problem
 and some possible solutions; it is a PR from the user's non-main branch into
@@ -1042,6 +1047,8 @@ it can serve as a useful example of what to expect from the PR review process.
 .. _open a new issue: https://github.com/mne-tools/mne-python/issues/new/choose
 .. _This sample pull request: https://github.com/mne-tools/mne-python/pull/6230
 .. _our user forum: https://mne.discourse.group
+.. _sg_execution_times page: https://mne.tools/dev/sg_execution_times.html
+.. _sg_api_usage page: https://mne.tools/dev/sg_api_usage.html
 
 .. git installation