docs: add map ops

ibis/expr/operations/maps.py

@@ -10,6 +10,8 @@
 
 @public
 class Map(Value):
+    """Construct a map."""
+
     keys: Value[dt.Array]
     values: Value[dt.Array]
 
@@ -25,12 +27,16 @@ def dtype(self):
 
 @public
 class MapLength(Unary):
+    """Compute the number of unique keys in a map."""
+
     arg: Value[dt.Map]
     dtype = dt.int64
 
 
 @public
 class MapGet(Value):
+    """Get a value from a map by key."""
+
     arg: Value[dt.Map]
     key: Value
     default: Value = None
@@ -44,6 +50,8 @@ def dtype(self):
 
 @public
 class MapContains(Value):
+    """Check if a map contains a key."""
+
     arg: Value[dt.Map]
     key: Value
 
@@ -53,6 +61,8 @@ class MapContains(Value):
 
 @public
 class MapKeys(Unary):
+    """Get the keys of a map as an array."""
+
     arg: Value[dt.Map]
 
     @attribute
@@ -62,6 +72,8 @@ def dtype(self):
 
 @public
 class MapValues(Unary):
+    """Get the values of a map as an array."""
+
     arg: Value[dt.Map]
 
     @attribute
@@ -71,6 +83,11 @@ def dtype(self):
 
 @public
 class MapMerge(Value):
+    """Combine two maps into one.
+
+    If a key is present in both maps, the value from the first is kept.
+    """
+
     left: Value[dt.Map]
     right: Value[dt.Map]