class_docstr: Base connector class to be extended by all connectors.
docstr: Populate the configuration dictionary with values from environment variables
  if not exists in the config.
  
  Args:
      config (dict): The configuration dictionary to be populated.
      envs_mapping (dict): The dictionary representing a map of config's keys
          and according names of the environment variables.
  
  Returns:
      dict: The populated configuration dictionary.
code: def _populate_config_from_env(self, config: dict, envs_mapping: dict):
      """
      Populate the configuration dictionary with values from environment variables
      if not exists in the config.
  
      Args:
          config (dict): The configuration dictionary to be populated.
          envs_mapping (dict): The dictionary representing a map of config's keys
              and according names of the environment variables.
  
      Returns:
          dict: The populated configuration dictionary.
      """
  
      for key, env_var in envs_mapping.items():
          if key not in config and os.getenv(env_var):
              config[key] = os.getenv(env_var)
  
      return config
  
imports: from abc import ABC, abstractmethod
  import os
  from ..helpers.df_info import DataFrameType
  from ..helpers.logger import Logger
  from pydantic import BaseModel
  from typing import Optional, Union
label_desc: Use image node_id 3 for calling the BaseConnector obj's underlying member method code with example usage: obj._populate_config_from_env(config, envs_mapping) and returns: config