<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def FindFieldByName(self, full_name):
 """Loads the named field descriptor from the pool. Args: full_name: The full name of the field descriptor to load. Returns: The field descriptor for the named field. Raises: KeyError: if the field cannot be found in the pool. """

    full_name = _NormalizeFullyQualifiedName(full_name)
    message_name, _, field_name = full_name.rpartition('.')
    message_descriptor = self.FindMessageTypeByName(message_name)
    return message_descriptor.fields_by_name[field_name]