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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 freeze():
 """Combine all dependencies for the Agent's static environment."""

    echo_waiting('Verifying collected packages...')
    catalog, errors = make_catalog()
    if errors:
        for error in errors:
            echo_failure(error)
        abort()

    static_file = get_agent_requirements()

    echo_info('Static file: {}'.format(static_file))

    pre_packages = list(read_packages(static_file))

    catalog.write_packages(static_file)

    post_packages = list(read_packages(static_file))
    display_package_changes(pre_packages, post_packages)