<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def float64(name, description, default=None):
 # type: (AName, ADescription, AFloat64Default) -> AAnno """Add a float64 parameter to be passed when instantiating this YAML file"""

    args = common_args(name, default)
    return Anno(description, typ=float, **args)