class_docstr: Create a new alias as a key-value pair. All aliases are stored
  in ``Alias.aliases``. Duplicate keys or values are not allowed,
  unless the ``replace`` parameter is ``True``.
  
  Parameters
  ----------
  name : str
      Alias key.
  expr : str
      Alias value.
  replace : bool, optional
      Replace the current key-value pair if it already exists.
  
  Attributes
  ----------
  Alias.aliases : dict
      Class variable for storing all known aliases
  
  Examples
  --------
  
  >>> Alias('atr', 'ma_truerange')
  >>> Alias('hc', 'higher_close')
code: def __init__(self, name, expr, replace=False):
      # code
      self.name = name
      self.expr = expr
      # add key with expression
      Alias.aliases[name] = expr
  
file_path: AlphaPy/alphapy/alias.py
imports: import logging
  import parser
  import re
label_desc: Use image node_id 2 to create a new Alias object from inherited base classes: object with example: obj = Alias(name, expr, replace)