Change PODLayer name (#251)

* rename PODBlock
* add tutorial rst

---------

Co-authored-by: Dario Coscia <dariocoscia@Dario-Coscia.local>
Co-authored-by: Dario Coscia <dariocoscia@Dario-Coscia.lan>

pina/model/layers/__init__.py

@@ -8,7 +8,7 @@ __all__ = [
     "FourierBlock1D",
     "FourierBlock2D",
     "FourierBlock3D",
-    "PODLayer",
+    "PODBlock",
 ]
 
 from .convolution_2d import ContinuousConvBlock
@@ -19,4 +19,4 @@ from .spectral import (
     SpectralConvBlock3D,
 )
 from .fourier import FourierBlock1D, FourierBlock2D, FourierBlock3D
-from .pod import PODLayer
+from .pod import PODBlock

pina/model/layers/pod.py

@@ -6,7 +6,7 @@ from .stride import Stride
 from .utils_convolution import optimizing
 
 
-class PODLayer(torch.nn.Module):
+class PODBlock(torch.nn.Module):
     """
     POD layer: it projects the input field on the proper orthogonal
     decomposition basis.  It needs to be fitted to the data before being used