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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 heads(directory=None, verbose=False, resolve_dependencies=False):
 """Show current available heads in the script directory"""

    if alembic_version >= (0, 7, 0):
        config = current_app.extensions['migrate'].migrate.get_config(
            directory)
        command.heads(config, verbose=verbose,
                      resolve_dependencies=resolve_dependencies)
    else:
        raise RuntimeError('Alembic 0.7.0 or greater is required')