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"""
Constraints for the requirements-and-capabilities matching mechanism.
"""

class NodeTemplateConstraint(object):
    """
    Used to constrain requirements for node templates.

    Must be serializable.
    """

    def matches(self, source_node_template, target_node_template):
        """
        Returns ``True`` if the target matches the constraint for the source.
        """
        raise NotImplementedError