Examples: Missed some 'epochs' occurrences (#1477)

Author: Saransh-cpp

docs/demos/pinn_forward/heat.resample.rst

@@ -110,7 +110,7 @@ We then train the model for 20000 iterations:
 
 .. code-block:: python
 
-    losshistory, train_state = model.train(epochs=200000, callbacks=[pde_resampler])
+    losshistory, train_state = model.train(iterations=200000, callbacks=[pde_resampler])
     
 After we train the network using Adam, we continue to train the network using L-BFGS to achieve a smaller loss:
 

docs/demos/pinn_forward/helmholtz.2d.sound.hard.abc.rst

@@ -67,7 +67,7 @@ Then, we begin by defining the general parameters for the problem. The PINN will
 .. code-block:: python
 
   weights = 1
-  epochs = 10000
+  iterations = 10000
   learning_rate = 1e-3
   num_dense_layers = 3
   num_dense_nodes = 350
@@ -216,7 +216,7 @@ We first train the model for 5000 iterations with Adam optimizer:
 
 .. code-block:: python
 
-    losshistory, train_state = model.train(epochs=epochs)
+    losshistory, train_state = model.train(iterations=iterations)
 
 
 Complete code

docs/demos/pinn_inverse/lorenz.inverse.rst

@@ -124,7 +124,7 @@ We then train the model for 60000 iterations:
 
 .. code-block:: python
 
-    losshistory, train_state = model.train(epochs=60000, callbacks=[variable])
+    losshistory, train_state = model.train(iterations=60000, callbacks=[variable])
 
 Complete code
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