chore: add get_string alias for Poscar

Author: timurbazhirov

pymatgen/io/vasp/inputs.py

@@ -584,6 +584,8 @@ def get_str(self, direct: bool = True, vasp4_compatible: bool = False, significa
 
         return "\n".join(lines) + "\n"
 
+    get_string = get_str
+
     def __repr__(self):
         return self.get_str()