Fix circular imports in knowledge utilities

pyrobosim/pyrobosim/core/world.py

@@ -51,6 +51,7 @@ def __init__(
         self.hallways = []
         self.locations = []
         self.objects = []
+        self.set_metadata()
 
         # Counters
         self.num_rooms = 0

pyrobosim/pyrobosim/utils/general.py

@@ -40,9 +40,16 @@ def __init__(self, filename):
         :param filename: Path to metadata YAML file.
         :type filename: str
         """
-        self.filename = filename
-        with open(self.filename) as file:
-            self.data = yaml.load(file, Loader=yaml.FullLoader)
+        if filename:
+            if not os.path.isfile(filename):
+                raise FileNotFoundError(f"Metadata filename not found: {filename}")
+
+            self.filename = filename
+            with open(self.filename) as file:
+                self.data = yaml.load(file, Loader=yaml.FullLoader)
+        else:
+            self.filename = None
+            self.data = {}
 
     def has_category(self, category):
         """

pyrobosim/pyrobosim/utils/knowledge.py

@@ -7,9 +7,6 @@
 import warnings
 import numpy as np
 
-from ..core.locations import Location, ObjectSpawn
-from ..core.objects import Object
-
 
 def apply_resolution_strategy(world, entity_list, resolution_strategy, robot=None):
     """
@@ -75,6 +72,9 @@ def query_to_entity(world, query_list, mode, resolution_strategy="first", robot=
     :return: The entity that meets the mode and resolution strategy, or None.
     :rtype: Entity
     """
+    from ..core.locations import Location, ObjectSpawn
+    from ..core.objects import Object
+
     room = None
     named_location = None
     loc_category = None
@@ -208,6 +208,8 @@ def resolve_to_location(
     :return: The location or object spawn that meets the category and/or room filters, or None.
     :rtype: :class:`pyrobosim.core.locations.Location`/:class:`pyrobosim.core.locations.ObjectSpawn`
     """
+    from ..core.locations import Location
+
     if room is None:
         room_name = None
         if category is None: