class_docstr: Simple matching estimator for binary treatments based on a distance
  metric.
  
  Supports additional parameters as listed below.
code: def construct_symbolic_estimator(self, estimand):
      expr = "b: " + ", ".join(estimand.outcome_variable) + "~"
      var_list = (
          estimand.treatment_variable
          + estimand.get_backdoor_variables()
      )
      expr += "+".join(var_list)
      return expr
  
file_path: dowhy/dowhy/causal_estimators/distance_matching_estimator.py
imports: from typing import Any, List, Optional, Union
  import numpy
  import pandas
  from sklearn.neighbors import NearestNeighbors
  from dowhy.causal_estimator import CausalEstimate, CausalEstimator
  from dowhy.causal_identifier import IdentifiedEstimand
label_desc: Use image node_id 4 for calling the DistanceMatchingEstimator obj's underlying member method code with example usage: obj.construct_symbolic_estimator(estimand) and returns: expr