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# BranchLengthEstimator.py

## High-level description

This code defines an abstract base class `BranchLengthEstimator` for branch length estimation algorithms in the Cassiopeia framework. It serves as a template for concrete branch length estimation algorithms, requiring them to implement the `estimate_branch_lengths` method.

## Code Structure

The `BranchLengthEstimator` class is an abstract base class defined using the `abc` module. It has a single abstract method, `estimate_branch_lengths`, which needs to be implemented by concrete subclasses.

## Symbols

### Symbol Name: `BranchLengthEstimator`

#### Description

This is an abstract base class for all branch length estimation algorithms. It defines a common interface for these algorithms, ensuring that they all have an `estimate_branch_lengths` method.

#### Inputs

The class itself does not take any inputs during initialization.

#### Outputs

The class itself does not return any outputs.

#### Internal Logic

This is an abstract base class and does not have any internal logic.

### Symbol Name: `estimate_branch_lengths`

#### Description

This is an abstract method that needs to be implemented by subclasses. It should estimate the branch lengths of a given tree.

#### Inputs

| Name | Type           | Description                                                                           |
| :--- | :------------- | :------------------------------------------------------------------------------------ |
| tree | CassiopeiaTree | CassiopeiaTree object storing character information and an initialized tree topology. |

#### Outputs

This method does not return any values. It should modify the input `tree` object in-place, updating the branch lengths.

#### Internal Logic

The internal logic of this method is specific to the concrete subclass that implements it.