class_docstr: Entry for Density Matrix (DM)
  The density matrix is used to express total energy of both non-interacting and
  interacting systems.
  
  Notes
  -----
  dm entry can only have 1 system
class_docstr_tok: ["Entry","for","Density","Matrix","(","DM",")","The","density","matrix","is","used","to","express","total","energy","of","both","non-interacting","and","interacting","systems",".","Notes","--","--","-","dm","entry","can","only","have","1","system"]
docstr: Parameters
  ----------
  e_type: str
  true_val: str
     must be a .npy file containing the pre-calculated density matrix
  systems: List[Dict]
docstr_tok: ["Parameters","--","--","--","--","--","e_type",":","str","true_val",":","str","must","be","a",".npy","file","containing","the","pre-calculated","density","matrix","systems",":","List","[","Dict","]"]
code: def __init__(self, e_type, true_val, systems, weight):
      """
      Parameters
      ----------
      e_type: str
      true_val: str
         must be a .npy file containing the pre-calculated density matrix
      systems: List[Dict]
  
      """
      super().__init__(e_type, true_val, systems)
      self.true_val = true_val
      assert len(self.get_systems()) == 1
      self._weight = weight
  
imports: from __future__ import annotations
  from abc import abstractmethod, abstractproperty
  from typing import List, Dict, Optional
  import numpy
  from dqc.system.mol import Mol
  from dqc.system.base_system import BaseSystem
  from deepchem.utils.dftutils import KSCalc
  from deepchem.utils.dft_utils import parse_moldesc, BaseGrid
label_desc: Use image node_id 1 to create a new _EntryDM object from inherited base classes: DFTEntry with example: obj = _EntryDM(e_type, true_val, systems, weight)