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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 _build_command(self, python_executable, lib_dir_fq, proxy_enabled):
 """Build the pip command for installing dependencies. Args: python_executable (str):
 The fully qualified path of the Python executable. lib_dir_fq (str):
 The fully qualified path of the lib directory. Returns: list: The Python pip command with all required args. """

        exe_command = [
            os.path.expanduser(python_executable),
            '-m',
            'pip',
            'install',
            '-r',
            self.requirements_file,
            '--ignore-installed',
            '--quiet',
            '--target',
            lib_dir_fq,
        ]
        if self.args.no_cache_dir:
            exe_command.append('--no-cache-dir')

        if proxy_enabled:
            # trust the pypi hosts to avoid ssl errors
            trusted_hosts = ['pypi.org', 'pypi.python.org', 'files.pythonhosted.org']

            for host in trusted_hosts:
                exe_command.append('--trusted-host')
                exe_command.append(host)

        return exe_command