class_docstr: Main interface for accessing values from MCMC results.
  
  The core method to select values is `get_values`. The method
  to select sampler statistics is `get_sampler_stats`. Both kinds of
  values can also be accessed by indexing the MultiTrace object.
  Indexing can behave in four ways:
  
  1. Indexing with a variable or variable name (str) returns all
     values for that variable, combining values for all chains.
  
     >>> trace[varname]
  
     Slicing after the variable name can be used to burn and thin
     the samples.
  
     >>> trace[varname, 1000:]
  
     For convenience during interactive use, values can also be
     accessed using the variable as an attribute.
  
     >>> trace.varname
  
  2. Indexing with an integer returns a dictionary with values for
     each variable at the given index (corresponding to a single
     sampling iteration).
  
  3. Slicing with a range returns a new trace with the number of draws
     corresponding to the range.
  
  4. Indexing with the name of a sampler statistic that is not also
     the name of a variable returns those values from all chains.
     If there is more than one sampler that provides that statistic,
     the values are concatenated along a new axis.
  
  For any methods that require a single trace (e.g., taking the length
  of the MultiTrace instance, which returns the number of draws), the
  trace with the highest chain number is always used.
  
  Attributes
  ----------
  nchains: int
      Number of chains in the `MultiTrace`.
  chains: `List[int]`
      List of chain indices
  report: str
      Report on the sampling process.
  varnames: `List[str]`
      List of variable names in the trace(s)
class_docstr_tok: ["Main","interface","for","accessing","values","from","MCMC","results",".","The","core","method","to","select","values","is","`","get_values","`",".","The","method","to","select","sampler","statistics","is","`","get_sampler_stats","`",".","Both","kinds","of","values","can","also","be","accessed","by","indexing","the","MultiTrace","object",".","Indexing","can","behave","in","four","ways",":","1",".","Indexing","with","a","variable","or","variable","name","(","str",")","returns","all","values","for","that","variable",",","combining","values","for","all","chains",".",">",">",">","trace","[","varname","]","Slicing","after","the","variable","name","can","be","used","to","burn","and","thin","the","samples",".",">",">",">","trace","[","varname",",","1000",":","]","For","convenience","during","interactive","use",",","values","can","also","be","accessed","using","the","variable","as","an","attribute",".",">",">",">","trace.varname","2",".","Indexing","with","an","integer","returns","a","dictionary","with","values","for","each","variable","at","the","given","index","(","corresponding","to","a","single","sampling","iteration",")",".","3",".","Slicing","with","a","range","returns","a","new","trace","with","the","number","of","draws","corresponding","to","the","range",".","4",".","Indexing","with","the","name","of","a","sampler","statistic","that","is","not","also","the","name","of","a","variable","returns","those","values","from","all","chains",".","If","there","is","more","than","one","sampler","that","provides","that","statistic",",","the","values","are","concatenated","along","a","new","axis",".","For","any","methods","that","require","a","single","trace","(","e.g.",",","taking","the","length","of","the","MultiTrace","instance",",","which","returns","the","number","of","draws",")",",","the","trace","with","the","highest","chain","number","is","always","used",".","Attributes","--","--","--","--","--","nchains",":","int","Number","of","chains","in","the","`","MultiTrace","`",".","chains",":","`","List","[","int","]","`","List","of","chain","indices","report",":","str","Report","on","the","sampling","process",".","varnames",":","`","List","[","str","]","`","List","of","variable","names","in","the","trace","(","s",")"]
code: def __len__(self):
      chain = self.chains[-1]
      return len(self._straces[chain])
  
imports: import itertools
  import logging
  import warnings
  from abc import ABC
  from typing import Any, Dict, List, Mapping, Optional, Sequence, Set, Sized, Tuple, TypeVar, Union, cast
  import numpy
  from pymc.backends.report import SamplerReport
  from pymc.model import modelcontext
  from pymc.util import get_var_name
label_desc: Use image node_id 9 for calling the MultiTrace obj's underlying member method code with example usage: obj.__len__() and returns: len