pub fn from_block(mut self, block: BlockNumber) -> Self {
        self.filter.block_hash = None;
        self.filter.from_block = Some(block);
        self
    }
Sets `from_block`. The fields `from_block` and `block_hash` are
mutually exclusive. Setting `from_block` will clear a previously set
`block_hash`.
core/lib/basic_types/src/web3/mod.rs