Move ArrayTransform into geo

This is part of work towards OpenwaterHealth#166.
The standoff_transform that goes into virtual fit ought to have
units associated with it, since it may often be provided in transducer
native units which can be different from the volume RAS space units.
So at this point ArrayTransform is more generally useful and doesn't
belong in session.py.

Author: ebrahimebrahim

src/openlifu/db/session.py

@@ -9,25 +9,11 @@
 
 import numpy as np
 
-from openlifu.geo import Point
+from openlifu.geo import ArrayTransform, Point
 from openlifu.util.json import PYFUSEncoder
 from openlifu.util.strings import sanitize
 
 
-@dataclass
-class ArrayTransform:
-    """Class representing the transform on a transducer array to position it in space.
-    units:
-    """
-
-    matrix: np.ndarray
-    """4x4 affine transform matrix"""
-
-    units : str
-    """The units of the space on which to apply the transform matrix , e.g. "mm"
-    (In order to apply the transform to transducer points,
-    first represent the points in these units.)"""
-
 @dataclass
 class TransducerTrackingResult:
     """

src/openlifu/geo.py

@@ -139,6 +139,18 @@ def to_json(self, compact:bool) -> str:
             return json.dumps(self.to_dict(), indent=4)
 
 
+@dataclass
+class ArrayTransform:
+    """An affine transform with a unit string, often intended to represent how a transducer array is positionsed in space."""
+
+    matrix: np.ndarray
+    """4x4 affine transform matrix"""
+
+    units : str
+    """The units of the space on which to apply the transform matrix , e.g. "mm"
+    (In order to apply the transform to points, first represent the points in these units.)
+    """
+
 # === Tools to work with spherical coordinate systems ===
 
 def cartesian_to_spherical(x:float,y:float,z:float) -> Tuple[float, float, float]:

tests/test_database.py

@@ -13,10 +13,11 @@
 from helpers import dataclasses_are_equal
 from vtk import vtkImageData, vtkPolyData
 
-from openlifu import Point, Solution
+from openlifu import Solution
 from openlifu.db import Session, Subject, User
 from openlifu.db.database import Database, OnConflictOpts
-from openlifu.db.session import ArrayTransform, TransducerTrackingResult
+from openlifu.db.session import TransducerTrackingResult
+from openlifu.geo import ArrayTransform, Point
 from openlifu.photoscan import Photoscan
 from openlifu.plan import Protocol, Run
 from openlifu.xdc import Transducer