error: field expressions cannot have generic arguments
  --> src/lib.rs:12:23
   |
12 |     match m.downcast::<PyFloat> {
   |                       ^^^^^^^^^

error[E0615]: attempted to take value of method `downcast` on type `&pyo3::types::any::PyAny`
  |
help: use parentheses to call the method
  |
1 | ()use pyo3::prelude::*;
  | ^^

error[E0308]: mismatched types
  |
  = note:   expected enum `std::result::Result<&pyo3::types::floatob::PyFloat, pyo3::err::PyErr>`
          found unit type `()`