def add_modifications(self, mod_dict):
    for aa in self.seq:
        if (aa.position in mod_dict):
            for mod in mod_dict[aa.position]:
                aa.set_modification(mod)
def add_modifications(self, mod_dict):
    for aa in self.seq:
        if (aa.position in mod_dict):
            for mod in mod_dict[aa.position]:
                aa.set_modification(mod)