def set_python_version(self, python_version: str = None) -> None:
if python_version is None:<EOL><INDENT>self.pipfile.meta.requires.pop("<STR_LIT>")<EOL><DEDENT>else:<EOL><INDENT>if self.pipfile.meta.requires is None:<EOL><INDENT>self.pipfile.meta.requires = {}<EOL><DEDENT>self.pipfile.meta.requires["<STR_LIT>"] = python_version<EOL><DEDENT>
Set version of Python used in the project.