Add docs example on context resolver

Author: mielvds

docs/examples/context_resolver.py

@@ -0,0 +1,52 @@
+import json
+
+from cachetools import LRUCache
+
+from pyld import ContextResolver, DocumentLoader, jsonld
+
+CONTEXT_URL = "context://my-app/vocab"
+
+DOCUMENT_CACHE = {
+    CONTEXT_URL: {
+        "contentType": "application/ld+json",
+        "contextUrl": None,
+        "documentUrl": CONTEXT_URL,
+        "document": {
+            "@context": {
+                "name": "https://schema.org/name",
+                "homepage": {"@id": "https://schema.org/url", "@type": "@id"},
+            }
+        },
+    }
+}
+
+
+class CachedContextLoader(DocumentLoader):
+    def __init__(self, documents):
+        self.documents = documents
+        self.load_count = 0
+
+    def __call__(self, url, options):
+        self.load_count += 1
+        return self.documents[url]
+
+
+loader = CachedContextLoader(DOCUMENT_CACHE)
+resolved_context_cache = LRUCache(maxsize=1000)
+resolver = ContextResolver(
+    resolved_context_cache,
+    loader,
+    max_context_urls=20,
+)
+
+doc = {
+    "@context": CONTEXT_URL,
+    "name": "Example Person",
+    "homepage": "https://example.com/",
+}
+options = {"documentLoader": loader, "contextResolver": resolver}
+
+expanded = jsonld.expand(doc, options=options)
+jsonld.expand(doc, options=options)
+
+print(json.dumps({"contextLoads": loader.load_count, "expanded": expanded}, indent=2))