'Get the variable given a name if one exists or create a new one if missing.
Parameters
name : str
name of the variable
**kwargs :
more arguments that\'s passed to symbol.Variable'

def get(self, name, **kwargs):

    name = (self._prefix + name)
    if (name not in self._params):
        self._params[name] = symbol.Variable(name, **kwargs)
    return self._params[name]
