code: def filter_metadata(self, key):
          
          filtered = [field[key] for field in self.metadata if key in field]
          if len(filtered) == 0:
              raise KeyError("Key not found in metadata")
          return filtered
docs: Return a list of values for the metadata key from each field
          of the project's metadata.
  
          Parameters
          ----------
          key: str
              A known key in the metadata structure
  
          Returns
          -------
          filtered :
              attribute list from each field