Retrieve object type in string form in robot-framework

a  = {}
b = str(type(a))

How can one migrate the python code to robot framework. I tried this,

${type_obj}=    Evaluate    type(${a})
${type_str}=    Evaluate    str(${type_obj})

But it just broke with a syntax error as,

Evaluating expression 'str(<type 'dict'>)' failed: SyntaxError: invalid syntax (<string>, line 1)