code: def get_field_value(self, key, default=MISSING):
          
          meta_value = self.metadata.get(key)
          context_value = self.context.get(key)
  
          if context_value is not None:
              return context_value
          elif meta_value is not None:
              return meta_value
  
          return default
docs: Method to fetch a value from either the fields metadata or the
          schemas context, in that order.
  
          Args:
              key (str): The name of the key to grab the value for.
  
          Keyword Args:
              default (object, optional): If the value doesn't exist in the
                  schema's ``context`` or the field's ``metadata``, this value
                  will be returned. By default this will be ``MISSING``.
  
          Returns:
              object: This will be the correct value to use given the parameters.