test: adding test and empty function

Author: Luiskitsu

src/diffpy/morph/morphs/morphsqueeze.py

@@ -0,0 +1,36 @@
+from diffpy.morph.morphs.morph import LABEL_GR, LABEL_RA, Morph
+
+
+class MorphSqueeze(Morph):
+    """Squeeze the morph function.
+
+    This applies a polynomial to squeeze the morph non-linearly. The resulting
+    squeezed morph is interpolated to the (trimmed) target grid.
+    Only the overlapping region between the squeezed morph and the target
+    grid is used. The target is trimmed (or not) accordingly, and the final
+    outputs (morph and target) are returned on the same grid, defined by this
+    trimmed target range.
+
+    Configuration Variables
+    -----------------------
+    squeeze
+        list or array-like
+        Polynomial coefficients [a0, a1, ..., an] for the squeeze function.
+    """
+
+    # Define input output types
+    summary = "Squeeze morph by polynomial shift"
+    xinlabel = LABEL_RA
+    yinlabel = LABEL_GR
+    xoutlabel = LABEL_RA
+    youtlabel = LABEL_GR
+    parnames = ["squeeze"]
+
+    def morph(self, x_morph, y_morph, x_target, y_target):
+        Morph.morph(self, x_morph, y_morph, x_target, y_target)
+        if self.squeeze is None:
+            self.x_morph_out = self.x_morph_in
+            self.y_morph_out = self.y_morph_in
+            return self.xyallout
+
+        return self.xyallout