Add type annotations and tidy some docstrings

ciw/exactnode.py

@@ -1,39 +1,34 @@
+from typing import List
+
 from .node import Node
 from .arrival_node import ArrivalNode
-from decimal import Decimal, getcontext
+from decimal import Decimal
 from .server import Server
 
 
 class ExactNode(Node):
-    """
-    Inherits from the Node class, implements a more
-    precise version of addition to fix discrepencies
-    with floating point numbers.
+    """Exact numerical precision node.
+
+    This class inherits from the Node class, and
+    implements a more precise version of addition to
+    fix discrepencies with floating point numbers.
     """
 
     @property
-    def now(self):
-        """
-        Gets the current time
-        """
+    def now(self) -> Decimal:
+        """Get the current time."""
         return Decimal(self.simulation.current_time)
 
-    def create_starting_servers(self):
-        """
-        Initialise the servers
-        """
+    def create_starting_servers(self) -> List[Server]:
+        """Initialise the servers at this node."""
         return [Server(self, i + 1, Decimal("0.0")) for i in range(self.c)]
 
-    def increment_time(self, original, increment):
-        """
-        Increments the original time by the increment
-        """
+    def increment_time(self, original, increment) -> Decimal:
+        """Increment the original time by the increment."""
         return Decimal(str(original)) + Decimal(str(increment))
 
-    def get_service_time(self, ind):
-        """
-        Returns a service time for the given customer class
-        """
+    def get_service_time(self, ind) -> Decimal:
+        """Return a service time for the given customer class."""
         return Decimal(
             str(
                 self.simulation.service_times[self.id_number][
@@ -44,21 +39,25 @@ def get_service_time(self, ind):
 
 
 class ExactArrivalNode(ArrivalNode):
-    """
+    """Node with exact numerical time precision.
+
     Inherits from the ArrivalNode class, implements a
     more precise version of addition to fix discrepencies
     with floating point numbers.
     """
 
-    def increment_time(self, original, increment):
-        """
-        Increments the original time by the increment
-        """
+    def increment_time(self, original, increment) -> Decimal:
+        """Increment the original time by the increment."""
         return Decimal(str(original)) + Decimal(str(increment))
 
-    def inter_arrival(self, nd, clss):
-        """
-        Samples the inter-arrival time for next class and node.
+    def inter_arrival(self, nd, clss) -> Decimal:
+        """Samples the inter-arrival time for next class and node.
+
+        Parameters
+        ----------
+        nd (Node): Next node.
+        clss (Individual): Individual class to be selected next.
+
         """
         return Decimal(
             str(