def __init__(
      self,
      *,
      label: VariableLabel,
      value: T,
      metadata: dict[Any, Any] | None = None,
  ):
    """Constructs a new variable.

    Args:
      label: The unique label for this variable.
      value: The initial value of the variable.
      metadata: A dictionary of metadata associated with this Variable.
    """
    self.label = label
    self.metadata = metadata or {}
    self.value = value
Constructs a new variable.

    Args:
      label: The unique label for this variable.
      value: The initial value of the variable.
      metadata: A dictionary of metadata associated with this Variable.
    
penzai/core/variables.py