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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 nodes_minimum_distance_validation(self):
 """ if minimum distance is specified, ensure node is not too close to other nodes; """

    if self.layer and self.layer.nodes_minimum_distance:
        minimum_distance = self.layer.nodes_minimum_distance
        # TODO - lower priority: do this check only when coordinates are changing
        near_nodes = Node.objects.exclude(pk=self.id).filter(geometry__distance_lte=(self.geometry, D(m=minimum_distance))).count()
        if near_nodes > 0:
            raise ValidationError(_('Distance between nodes cannot be less than %s meters') % minimum_distance)