feat(Field): add VertexField to support data at vertices

discretisedfield/vertex_field.py

@@ -0,0 +1,44 @@
+from discretisedfield import Field
+
+
+class VertexField(Field):
+    def _repr_html_(self):
+        pass  # @Martin
+
+    def __call__(self, point):
+        raise NotImplementedError
+
+    def diff(self, direction, order=1, restrict2valid=True):
+        """Maybe this is slighly wrong and we should ask Claas about this."""
+        super().diff(direction, order=order, restrict2valid=restrict2valid)
+
+    def integrate(self, direction=None, cumulative=False):
+        """Maybe this is slighly wrong and we should ask Claas about this."""
+        super().integrate(direction=direction, cumulative=cumulative)
+
+    def line(self, p1, p2, n):
+        pass  # @Martin
+
+    def __getitem__(self, item):
+        raise NotImplementedError
+
+    def to_vtk(self):
+        pass  # @Martin
+
+    def mpl(self):
+        pass  # @Swapneel
+
+    def hv(self):
+        pass  # @Swapneel
+
+    # NOTE: We are ignoring all the FFTs for now.
+
+    def to_xarray(self, name="field", unit=None):
+        pass  # @Swapneel
+
+    @classmethod
+    def from_xarray(cls, xa):
+        raise NotImplementedError
+
+
+# TODO: reimplement the _as_array functions. @Swapneel