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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_command_signature(self, command):
 """Retrieves the signature portion of the help page. Parameters command: :class:`Command` The command to get the signature of. Returns -------- :class:`str` The signature for the command. """


        parent = command.full_parent_name
        if len(command.aliases) > 0:
            aliases = '|'.join(command.aliases)
            fmt = '[%s|%s]' % (command.name, aliases)
            if parent:
                fmt = parent + ' ' + fmt
            alias = fmt
        else:
            alias = command.name if not parent else parent + ' ' + command.name

        return '%s%s %s' % (self.clean_prefix, alias, command.signature)