'Find variables covering the given region offset.
:param int start:
:return: A list of stack variables.
:rtype:  set'

def get_variables_by_offset(self, start):

    try:
        base_addr = self._storage.floor_key(start)
    except KeyError:
        return []
    item = self._storage[base_addr]
    if item.includes(start):
        return item.variables
    return []
