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myenv/Lib/site-packages/pip/_internal/distributions/base.py

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+import abc
+
+from pip._vendor.six import add_metaclass
+
+
+@add_metaclass(abc.ABCMeta)
+class AbstractDistribution(object):
+    """A base class for handling installable artifacts.
+
+    The requirements for anything installable are as follows:
+
+     - we must be able to determine the requirement name
+       (or we can't correctly handle the non-upgrade case).
+
+     - for packages with setup requirements, we must also be able
+       to determine their requirements without installing additional
+       packages (for the same reason as run-time dependencies)
+
+     - we must be able to create a Distribution object exposing the
+       above metadata.
+    """
+
+    def __init__(self, req):
+        super(AbstractDistribution, self).__init__()
+        self.req = req
+
+    @abc.abstractmethod
+    def get_pkg_resources_distribution(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def prepare_distribution_metadata(self, finder, build_isolation):
+        raise NotImplementedError()