class_docstr: Abstract base class for calculating when futures contracts are the active
  contract.
class_docstr_tok: ["Abstract","base","class","for","calculating","when","futures","contracts","are","the","active","contract","."]
docstr: Parameters
  ----------
  root_symbol : str
      The root symbol for the contract chain.
  dt : Timestamp
      The datetime for which to retrieve the current contract.
  offset : int
      The offset from the primary contract.
      0 is the primary, 1 is the secondary, etc.
  
  Returns
  -------
  Future
      The active future contract at the given dt.
docstr_tok: ["Parameters","--","--","--","--","--","root_symbol",":","str","The","root","symbol","for","the","contract","chain",".","dt",":","Timestamp","The","datetime","for","which","to","retrieve","the","current","contract",".","offset",":","int","The","offset","from","the","primary","contract",".","0","is","the","primary",",","1","is","the","secondary",",","etc",".","Returns","--","--","--","-","Future","The","active","future","contract","at","the","given","dt","."]
code: def get_contract_center(self, root_symbol, dt, offset):
      """
      Parameters
      ----------
      root_symbol : str
          The root symbol for the contract chain.
      dt : Timestamp
          The datetime for which to retrieve the current contract.
      offset : int
          The offset from the primary contract.
          0 is the primary, 1 is the secondary, etc.
  
      Returns
      -------
      Future
          The active future contract at the given dt.
      """
      return self._get_active_contract_at_offset(
          root_symbol, dt, offset
      )
  
file_path: zipline/zipline/assets/roll_finder.py
imports: from abc import ABCMeta, abstractmethod
  from six import with_metaclass
label_desc: Use image node_id 3 for calling the RollFinder obj's underlying member method code with example usage: obj.get_contract_center(root_symbol, dt, offset) and returns: self