[E-node < E-idora-node] Add docs for node procedure

mage/query-modules/cpp/node.md

@@ -77,6 +77,42 @@ MATCH (intern:Intern) CALL node.relationship_types(intern, ["<KNOWS", "SEES>", "
 +--------------------------------+
 ```
 
+### `relationship_exists(node, pattern)`
+
+Checks if given node has a relationship of the pattern.  
+
+#### Input:
+
+- `node: Node` ➡ node for which relationship existance is to be verified.
+- `pattern: List[string] (optional)` ➡ list of relationship types for which it will be checked if at least one of them exists; if nothing is stated, procedure checks all types of relationships.
+
+:::info
+
+If '<' is added in front of the relationship type, only relationships coming into the node will be checked (e.g., "<KNOWS"), while if '>' is added at the end of the relationship type, only relationships coming from the node will be checked (e.g., "KNOWS>").
+Furthermore, if relationship type is not relevant, it is possible to enter only "<" or ">" to check ingoing or outgoing relationships.
+
+:::
+
+#### Output:
+
+- `exists: bool` ➡ whether or not provided node has a relationship of specified type.
+
+#### Usage:
+
+```cypher
+MERGE (a:Person {name: "Phoebe"}) MERGE (b:Person {name: "Joey"}) CREATE (a)-[f:FRIENDS]->(b);
+MATCH (a:Person {name: "Joey"}) CALL node.relationship_exists(a, ["<FRIENDS"]) 
+YIELD exists RETURN exists;
+```
+
+```plaintext
++----------------------------+
+| exists                     |
++----------------------------+
+| True                       |
++----------------------------+
+```
+
 
 ### `relationships_exist(node, relationships)`
 
@@ -124,4 +160,3 @@ MATCH (h:Human) CALL node.relationships_exist(h, ["LOVES>", "TAKES_CARE_OF", "FO
 | {"<LOVES": true, "FOLLOWS": false, "LOVES>": false, "TAKES_CARE_OF": true} |                  
 +----------------------------------------------------------------------------+
 ```
-