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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 _AcquireLock(self, urn, blocking=None, blocking_lock_timeout=None, lease_time=None, blocking_sleep_interval=None):
 """This actually acquires the lock for a given URN."""

    if urn is None:
      raise ValueError("URN cannot be None")

    urn = rdfvalue.RDFURN(urn)

    try:
      return data_store.DB.LockRetryWrapper(
          urn,
          retrywrap_timeout=blocking_sleep_interval,
          retrywrap_max_timeout=blocking_lock_timeout,
          blocking=blocking,
          lease_time=lease_time)
    except data_store.DBSubjectLockError as e:
      raise LockError(e)