code: def validate_constraints(self):
          
          constraints = self.get_constraints()
          for constraint in constraints:
              try:
                  constraint.check_if_exists(False)
              except Exception:
                  from pipenv.exceptions import DependencyConflict
                  msg = (
                      "Cannot resolve conflicting version {0}{1} while {1}{2} is "
                      "locked.".format(
                          self.name, self.updated_specifier, self.old_name, self.old_specifiers
                      )
                  )
                  raise DependencyConflict(msg)
          return True
docs: Retrieves the full set of available constraints and iterate over them, validating
          that they exist and that they are not causing unresolvable conflicts.
  
          :return: True if the constraints are satisfied by the resolution provided
          :raises: :exc:`pipenv.exceptions.DependencyConflict` if the constraints dont exist