async def change_prefix(self, ctx, prefix: CheckLength.check_length):
"""Changes server's command prefix
:param ctx: the context in which a command is called
:type ctx: discord.ext.commands.Context
:param prefix: new prefix which invokes commands
:type prefix: str
"""
old_prefix = \
Database.get_one(Database.db_servers, {'_id': ctx.guild.id}, selection={'settings.prefix': 1, '_id': 0})[
'settings']['prefix']
# Zapytanie w MongoDB, aby wejsc glebiej do slownika po kluczach uzywamy '.'
if Database.update_one(Database.db_servers, {'_id': ctx.guild.id}, {'settings.prefix': prefix}):
await ctx.send(f'Pomyślnie zmienio prefix z {old_prefix} na {prefix}')
