if (c == 0) return os << "\t\tvacío\n";
for (unsigned i = 0; i < c; ++i)
os << "\t\t" << im.keys(i) << ":\t" << *im[i] << "\n";
return os;
if (c == 0) return os << "\t\tvacío\n";
for (unsigned i = 0; i < c; ++i)
os << "\t\t" << im.keys(i) << ":\t" << *im[i] << "\n";
return os;