Use poscar write as string.

dev-requirements.txt

@@ -110,7 +110,7 @@ requests-oauthlib>=1.3.0
 retworkx>=0.10.2
 rsa>=4.8
 scikit-image>=0.19.1
-scikit-learn==0.22
+scikit-learn==0.22.1
 #scikit-learn==1.0.1
 scipy>=1.10.1
 semantic-version>=2.6.0