fix: expressions plugin doctests

Author: yaugenst-flex

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Regression in local field projection leading to incorrect results for `far_field_approx=True`.
 - Bug when differentiating with respect to `Cylinder.center`.
 - `xarray` 2024.10.0 compatibility for autograd.
+- Some failing examples in the expressions plugin documentation.
 
 
 ## [2.7.6] - 2024-10-30

tidy3d/plugins/expressions/metrics.py

@@ -54,10 +54,12 @@ class ModeAmp(Metric):
 
     Examples
     --------
-    >>> monitor = ModeMonitor(name="monitor1", f=[1.0])
+    >>> import tidy3d as td
+    >>> monitor = td.ModeMonitor(size=(1, 1, 0), freqs=[2e14], mode_spec=td.ModeSpec(), name="monitor1")
     >>> mode_coeff = ModeAmp.from_mode_monitor(monitor)
-    >>> data = SimulationData()  # Assume this is a valid SimulationData object
-    >>> result = mode_coeff.evaluate(data)
+    >>> expr = abs(mode_coeff) ** 2
+    >>> print(expr)
+    (abs(ModeAmp("monitor1")) ** 2)
     """
 
     monitor_name: str = pd.Field(
@@ -122,10 +124,9 @@ class ModePower(ModeAmp):
 
     Examples
     --------
-    >>> monitor = ModeMonitor(name="monitor1", f=[1.0])
+    >>> import tidy3d as td
+    >>> monitor = td.ModeMonitor(size=(1, 1, 0), freqs=[2e14], mode_spec=td.ModeSpec(), name="monitor1")
     >>> mode_power = ModePower.from_mode_monitor(monitor)
-    >>> data = SimulationData()  # Assume this is a valid SimulationData object
-    >>> result = mode_power.evaluate(data)
     """
 
     def evaluate(self, *args: Any, **kwargs: Any) -> NumberType:

tidy3d/plugins/expressions/variables.py

@@ -29,11 +29,12 @@ class Variable(Expression):
 
     Examples
     --------
-    >>> x = Variable()
+    >>> x = Variable()  # unnamed
     >>> y = Variable(name='y')
-    >>> expr = x + y
-    >>> expr(5, y=3)  # Returns 8
-    >>> expr(5, 3)    # Raises ValueError
+    >>> z = Variable(name='z')
+    >>> expr = x + y + z
+    >>> expr(5, y=3, z=2)
+    10
     """
 
     name: Optional[str] = pd.Field(
@@ -75,7 +76,8 @@ class Constant(Variable):
     Examples
     --------
     >>> c = Constant(5)
-    >>> c.evaluate()  # Returns 5
+    >>> c.evaluate()
+    5
     """
 
     value: NumberType = pd.Field(