def fn_float64(self, value):
if is_ndarray(value) or isinstance(value, (list, tuple)):<EOL><INDENT>return self._to_ndarray(value).astype('<STR_LIT>')<EOL><DEDENT>else:<EOL><INDENT>return float(value)<EOL><DEDENT>
Return the value cast to a 64-bit float (numpy array) or a Python float (single value).

:param value: The number.
:return: The number as a float.