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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 SetCredentials(self, password=None, username=None):
 """Sets the database credentials. Args: password (Optional[str]):
 password to access the database. username (Optional[str]):
 username to access the database. """

    if password:
      self._password = password
    if username:
      self._user = username