code: def BuildFindSpecs(self, environment_variables=None):
      
      path_attributes = {}
      if environment_variables:
        for environment_variable in environment_variables:
          attribute_name = environment_variable.name.lower()
          attribute_value = environment_variable.value
          if not isinstance(attribute_value, py2to3.STRING_TYPES):
            continue
  
          # Remove the drive letter.
          if len(attribute_value) > 2 and attribute_value[1] == ':':
            _, _, attribute_value = attribute_value.rpartition(':')
  
          if attribute_value.startswith('\\'):
            attribute_value = attribute_value.replace('\\', '/')
  
          path_attributes[attribute_name] = attribute_value
  
      find_specs = []
      with open(self._path, 'r') as file_object:
        for line in file_object:
          line = line.strip()
          if line.startswith('#'):
            continue
  
          if path_attributes:
            try:
              line = line.format(**path_attributes)
            except KeyError as exception:
              logger.error((
                  'Unable to expand path filter: {0:s} with error: '
                  '{1!s}').format(line, exception))
              continue
  
          if not line.startswith('/'):
            logger.warning((
                'The path filter must be defined as an absolute path: '
                '{0:s}').format(line))
            continue
  
          # Convert the path filters into a list of path segments and strip
          # the root path segment.
          path_segments = line.split('/')
          path_segments.pop(0)
  
          if not path_segments[-1]:
            logger.warning(
                'Empty last path segment in path filter: {0:s}'.format(line))
            continue
  
          find_spec = file_system_searcher.FindSpec(
              location_regex=path_segments, case_sensitive=False)
          find_specs.append(find_spec)
  
      return find_specs
docs: Build find specification from a filter file.
  
      Args:
        environment_variables (Optional[list[EnvironmentVariableArtifact]]):
            environment variables.
  
      Returns:
        list[dfvfs.FindSpec]: find specification.