elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
return -cls._fromast(node.operand)
elif isinstance(node, ast.BinOp):
elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
return -cls._fromast(node.operand)
elif isinstance(node, ast.BinOp):